A method for manufacturing a rigid-flexible composite board with an outer flexible substrate and POFV thereof

Abstract

The present invention belongs to the field of hard-soft boards, and in particular, to a hard-soft board with an outer flexible substrate and a method for making the POFV thereof. A method for making a hard-soft board with an outer flexible substrate and a method for making the POFV thereof. The hard-soft board with an outer flexible substrate includes a hard board with an n-layer structure, a flexible substrate is arranged between the upper and lower surfaces of the hard board, the hard board forms a connection dynamic zone through the connection of the flexible substrate, the upper surface of the flexible substrate and the lower surface located in the dynamic zone are covered with a covering film, and stripe grooves are evenly spaced on the surface of the covering film located in the dynamic zone away from the hard board. The use of a laminated plate structure of FR-4 substrate-silicone base film-plug hole substrate flexible surface-plug hole surface-resin aluminum sheet prevents the flexible substrate from deforming along the grinding direction during the grinding process, and prevents the flexible substrate from being polished uncleanly and exposing the substrate. The stripe grooves can release the pulling stress, prevent the covering film from breaking under greater stress, and increase the service life of the covering film.

Description

Technical Field

[0001] The invention belongs to the field of rigid-flexible boards, and in particular relates to a rigid-flexible board with an outer flexible substrate and a method for manufacturing the POFV thereof. Background Art

[0002] As electronic products become more and more lightweight and miniaturized, their functions are becoming more and more complete. Especially in the past two years, the three-dimensional installation and small space solutions of soft and hard circuit boards have been favored by many fields. In order to make the wiring space between layers wider and more free, many designs will directly arrange the vias or micro blind holes in the connection disk when considering space utilization. This structure is called VIP hole, which is what we often call plate-in-plate hole. Its manufacturing process is also called POFV (Plate OverFilled Via) process. VIP holes need to be mounted with components, so the pads after the resin plugging holes need to be copper-plated, and good flatness must be ensured. The process is the unique process of POFV.

[0003] At present, all PCB board factories use the following process when making POFV: pre-process - VIA drilling - copper deposition - VCP - resin plugging - curing - resin polishing - copper deposition 2 - VCP2 - post-process. First, the copper of the VIP hole is filled, and then the hole is filled with resin. Secondly, the protruding resin in the hole is polished flat with ceramic, and finally a layer of copper is electroplated on the polished board surface to complete the POFV process.

[0004] The structural type of the hard-soft board when the outer layer is a soft board, because the soft board substrate is composed of PI polyimide film and copper foil, the flexible substrate will deform along the grinding direction during the ceramic grinding process, and because the flexible board surface is uneven, the polishing will not be clean and the substrate will be exposed after grinding. Therefore, the traditional resin plugging and polishing and VCP electroplating process obviously cannot achieve the POFV process, and when deformation occurs, the transition zone between the hard boards connected by the flexible substrate will bend, also called the dynamic zone. In this case, the cover film attached to the upper and lower surfaces of the flexible substrate in the dynamic zone is easily pulled and deformed. Under repeated and long-term pulling, there will be a large stress that cannot be released, which is easy to cause the cover film to rupture, which will shorten the service life of the cover film and the service life of the circuit board. Summary of the invention

[0005] The embodiment of the present application provides a method for manufacturing a hard-soft combination board of an outer flexible substrate and its POFV, which can overcome the shortcomings that the flexible substrate will deform along the grinding direction during the ceramic grinding process and that the flexible substrate will not be polished cleanly and the substrate will be exposed after grinding due to the uneven surface of the flexible board, thereby realizing the POFV process. In addition, laser processing is used to open stripe grooves on the covering film in the dynamic area. When the covering film is pulled, the stripe grooves can release the pulling stress, thereby preventing the covering film from breaking under a large stress, thereby increasing the service life of the covering film.

[0006] The embodiment of the present application provides a hard-soft combination board with an outer flexible substrate, including a hard board with an n-layer structure, a flexible substrate for connecting the hard boards is arranged on the upper surface of the hard board, the hard board forms a connection dynamic area through the connection of the flexible substrate, the upper surface of the flexible substrate and the lower surface located in the dynamic area are covered with a covering film, the surface of the covering film located in the dynamic area away from the hard board is evenly spaced with stripe grooves, the hard board is opened with a first through hole and a second through hole, the first through hole passes through the hard board and the flexible substrate, both ends of the first through hole are provided with pads, and the second through hole passes through the hard board and is a mechanical buried hole.

[0007] The embodiment of the present application also provides a method for manufacturing a POFV of a flexible and rigid combination board of an outer flexible substrate, the manufacturing method comprising the following steps:

[0008] a. In the previous process, the inner core board is stacked with prepregs and riveted with pipe nails. Under a certain temperature and pressure, the resin of the prepreg flows and fills the circuit and substrate. When the temperature reaches a certain level, it solidifies and bonds the layers together to form a complete PCB.

[0009] b. VIA drilling: drilling is performed on the pressed board to prepare for the conduction of the inner and outer layers in the subsequent process;

[0010] c. Copper deposition: colloidal palladium is adsorbed on the surface and in the pores through activation, and an oxidation-reduction reaction occurs in the copper deposition tank, forming a 0.3-0.5um copper layer on the wall of the VIA pores;

[0011] d. VCP, thickening the copper thickness of the hole / surface copper by electrolysis;

[0012] e. Resin plugging: A vacuum plugging machine is used to fill the copper-plated VIA holes with resin. The stacking method of resin plugging is FR-4 board-silicone base film-plugging substrate flexible surface-plugging surface-resin aluminum sheet. The plugging surface is from the non-flexible surface and the knife pressure is adjusted according to the plate thickness-aperture ratio. The resin plugging process ensures that the resin does not 100% pop out of the plugging substrate flexible surface;

[0013] f. Curing: Curing the resin in the VIA hole by baking at high temperature to ensure that the resin in the hole reaches a relative hardness;

[0014] g. Resin polishing, polishing the excess resin at the VIA hole. The resin polishing is pre-polished using a ceramic polisher. The polishing only opens the cloth weaving and polishes from the single-sided flexible substrate surface. The cloth weaving current is 1.5A and the cloth weaving speed is 2.5 meters;

[0015] h. Copper deposition 2;

[0016] l. VCP2, using single-sided hole filling on the flexible side of the plug-hole substrate, and further double-sided copper plating, the copper plating thickness is flat and consistent with the hole thickness, and the double-sided copper plating is uniform and consistent;

[0017] m. Post-processing.

[0018] n. Laser cutting stripe grooves: a plurality of stripe grooves are evenly spaced on the surface of the cover film located in the dynamic area away from the hard board by using laser processing.

[0019] The beneficial effects of the present invention are as follows: 1. In step e, the traditional stacking structure of air guide plate-substrate-resin aluminum sheet is abandoned, and a stacking structure of FR-4 substrate-silicone base film-plugging substrate flexible surface-plugging surface-resin aluminum sheet is used. The holes are plugged from the non-flexible surface, and the bottom silicone base film can effectively prevent the high flow of resin, thereby preventing the flexible substrate from deforming along the grinding direction during the ceramic grinding process in step g.

[0020] 2. In step g, the ceramic grinding is only for the non-flexible substrate surface, which prevents the flexible substrate from being polished incompletely and exposing the substrate.

[0021] 3. Striped grooves are evenly spaced on the surface of the cover film in the dynamic area away from the hard board. The depth of the striped grooves is one-third of the thickness of the cover film. When the cover film is pulled, the striped grooves can release the pulling stress, thereby preventing the cover film from breaking under greater stress, thereby increasing the service life of the cover film and the soft-hard combination circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the present invention.

[0023] Among them, the above-mentioned drawings include the following figure marks: 1. hard board, 2. flexible substrate, 3. first through hole, 4. second through hole, 5. pad, 6. connection dynamic area, 7. covering film, 8. stripe groove. DETAILED DESCRIPTION

[0024] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0025] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs.

[0026] In the present invention, unless otherwise specified, the directional words used, such as "up" and "down", usually refer to the directions shown in the drawings, or to the vertical, perpendicular or gravity directions; similarly, for ease of understanding and description, "left" and "right" usually refer to the left and right shown in the drawings; "inside" and "outside" refer to the inside and outside relative to the outline of each component itself, but the above directional words are not used to limit the present invention.

[0027] In addition, in the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0028] In order to solve the technical problems in the prior art that the traditional process of using resin plugging followed by polishing and then VCP electroplating is obviously unable to realize the POFV process and the covering film will have a large stress that cannot be released under multiple and long-term pulling, which may easily cause the covering film to break, the embodiment of the present application provides a hard-soft combination board of an outer flexible substrate and a method for manufacturing POFV thereof.

[0029] The present invention is further described below in conjunction with the accompanying drawings.

[0030] like Figure 1 As shown, the present embodiment provides a hard-soft combination board with an outer flexible substrate, including a hard board 1 with an n-layer structure, a flexible substrate 2 for connecting the hard boards 1 is arranged on the upper surface of the hard board 1, and a connection dynamic area 6 is formed at the connection between the flexible substrate 2. The upper surface of the flexible substrate 2 and the lower surface located in the dynamic area are covered with a covering film 7, and the surface of the covering film 7 located in the dynamic area away from the side of the hard board 1 is evenly spaced with stripe grooves 8, and the hard board 1 is provided with a first through hole 3 and a second through hole 4, the first through hole 3 passes through the hard board 1 and the flexible substrate 2, and pads 5 are arranged at both ends of the first through hole 3, and the second through hole 4 passes through the hard board 1 and is a mechanical buried hole.

[0031] On the surface of the covering film 7 located in the dynamic zone away from the hard board 1, striped grooves 8 are evenly spaced. The depth of the striped grooves 8 is one third of the thickness of the covering film 7. When the covering film 7 is pulled, the striped grooves 8 can release the pulling stress, thereby preventing the covering film 7 from breaking under greater stress, thereby increasing the service life of the covering film 7.

[0032] This embodiment also provides a method for manufacturing a rigid-flexible board and POFV of an outer flexible substrate.

[0033] At present, all PCB board factories use the following process when making POFV: pre-process - VIA drilling - copper deposition - VCP - resin plugging - curing - resin polishing - copper deposition 2 - VCP2 - post-process. This process includes all POFV board making processes, and the process is irreplaceable. Therefore, in the soft-rigid combination board structure of the outer flexible substrate, the processing process is consistent with this. Because the outer flexible substrate cannot be resin polished, I have made adjustments to some of the processes, including the following points:

[0034] 1. The resin plugging hole uses vacuum plugging hole plus silicone film. The stacking method is FR-4 board-silicone film-plugging substrate flexible surface-plugging surface-resin aluminum sheet. The plugging surface is from the non-flexible surface, and the knife pressure is adjusted according to the plate thickness aperture ratio. The plugging process ensures that the resin does not 100% come out of the flexible surface. The silicone film at the bottom can effectively block the high fluidity of the resin, and control the fullness through its resin viscosity and pressure.

[0035] 2. Pre-curing after plugging, and then pre-grinding with a ceramic grinder. The grinding only opens the cloth and grinds the flexible substrate on one side. The cloth current is 1.5A, the speed is 2.5 meters, and the water pressure of the cloth grinding section is adjusted on one side, which mainly cleans the resin on the board surface. Afterwards, the resin is further cured by high temperature baking, and then ceramic grinding is used. The ceramic grinding brush and cloth are opened on one side, and the flexible substrate surface is not ground.

[0036] 3. In order to prevent the resin from sinking at the aperture of the flexible substrate, VCP2 in the process preferably fills the aperture on one side of the flexible surface, and further coats the aperture with copper on both sides. The copper plating thickness is consistent with the aperture thickness, and the copper plating on both sides is uniform.

[0037] 4. A plurality of evenly spaced stripe grooves 8 are provided on the cover film 7 of the rigid-flex board located in the dynamic area 6.

[0038] In the above improved process, we abandoned the traditional air guide plate-substrate-resin aluminum sheet, and used FR-4 substrate-silicone base film-plugging substrate flexible surface-plugging surface-resin aluminum sheet stacking structure, plugging from the non-flexible surface, the bottom silicone base film can effectively prevent the high flow of resin, and control the fullness of the plugging by adjusting the plugging pressure and resin viscosity. In addition, ceramic cloth is used to clean the flexible surface to prevent the resin board surface from remaining after high-temperature curing. The polishing after curing is only for the non-flexible substrate surface to prevent the flexible substrate from being polished and the substrate from being exposed. Single-sided hole filling can effectively improve the hole mouth depression, and it is also the last step of the outer flexible substrate hard-soft combined circuit board POFV. Through its process adjustment and process parameter control, this process can be effectively realized. Moreover, the present invention adopts a new vacuum resin plugging technology and polishing process, and the flexible layer adopts a hole plating + filling process to achieve POFV. Such a small-pitch outer layer flexible rigid-flexible circuit can be used for small-batch verification. In the final process, we use laser processing to open a number of evenly spaced stripe grooves 8 on the covering film 7 of the rigid-flexible board connecting the dynamic area 6, thereby further improving the service life of the covering film 7.

[0039] The above-mentioned embodiments only express the preferred implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present invention. It should be pointed out that, for a person skilled in the art, several modifications, improvements and substitutions can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the attached claims.

Claims

1. A method for manufacturing a POFV with an outer flexible substrate, which is applied to a POFV with an outer flexible substrate. The POFV with an outer flexible substrate comprises a hard board with an n-layer structure, a flexible substrate for connecting the hard boards is arranged on the upper surface of the hard board, and a dynamic area is formed by connecting the hard boards through the flexible substrate. The upper surface of the flexible substrate and the lower surface located in the dynamic area are covered with a covering film, and the surface of the covering film located in the dynamic area away from the hard board is evenly spaced with stripe grooves, characterized in that: The production method comprises the following steps: a. In the previous process, the inner core board is stacked with prepregs and riveted with pipe nails. Under a certain temperature and pressure, the resin of the prepreg flows and fills the circuit and substrate. When the temperature reaches a certain level, it solidifies and bonds the layers together to form a complete PCB. b. VIA drilling: drilling is performed on the pressed board to prepare for the conduction of the inner and outer layers in the subsequent process; c. Copper deposition: colloidal palladium is adsorbed on the surface and inside the pores through activation treatment, and an oxidation-reduction reaction occurs in the copper deposition tank, forming a 0.3-0.5um copper layer on the wall of the VIA pores; d. VCP, thickening the copper thickness of the hole / surface copper by electrolysis; e. Resin plugging: A vacuum plugging machine is used to fill the copper-plated VIA holes with resin. The stacking method of resin plugging is FR-4 board-silicone base film-plugging substrate flexible surface-plugging surface-resin aluminum sheet. The plugging surface is from the non-flexible surface and the knife pressure is adjusted according to the plate thickness-aperture ratio. The resin filling height is controlled during the resin plugging process so that it does not reach the flexible surface of the plugging substrate; f. Curing: Curing the resin in the VIA hole by baking at high temperature to ensure that the resin in the hole reaches a relative hardness; g. Resin polishing, polishing the excess resin at the VIA hole. The resin polishing is pre-polished using a ceramic grinder. The polishing only opens the non-woven fabric and polishes from a single side of the flexible substrate. The non-woven fabric current is 1.5A; h. Copper deposition 2; l. VCP2, using electroplating to fill the holes on one side of the flexible surface of the plug-hole substrate, and further plating copper on both sides to ensure that the copper plating thickness is flat and consistent with the hole thickness, and improve the uniformity of double-sided copper plating; m. Post-processing; n. Laser cutting stripe grooves: a plurality of stripe grooves are evenly spaced on the surface of the cover film located in the dynamic area away from the hard board by using laser processing.

2. The method for manufacturing a POFV with a flexible outer substrate according to claim 1, characterized in that: The hard plate is provided with a first through hole and a second through hole.

3. The method for manufacturing a POFV with a flexible outer substrate according to claim 2, characterized in that: The first through hole passes through the hard board and the flexible substrate, both ends of the first through hole are provided with pads, and the second through hole passes through the hard board and is a mechanical buried hole.

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