Manufacturing method of rigid-flex printed circuit board without vent holes

Abstract

The invention discloses a method for manufacturing a rigid-flex printed circuit board without vent holes, relates to the technical field of PCB (printed circuit board) processes, and can solve the problem of gas expansion layering without adopting a drilling method. The manufacturing method of the rigid-flex printed circuit board without the air hole comprises the following steps of lamination, primary copper reduction, primary drilling, primary copper deposition, resin hole plugging, baking after resistance welding, external light imaging, secondary copper reduction, alkaline etching, third copper reduction, secondary copper deposition, secondary drilling, third copper deposition, secondary external light imaging, copper tin plating and alkaline etching. The resin is cured through low-temperature resistance welding post-baking, gas in the cavity of the flexible area cannot expand due to heating, and then the problem of gas expansion layering is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of PCB process, and in particular to a method for manufacturing a rigid-flexible board without air holes. Background Art

[0002] During the production and processing of rigid-flex boards, air holes are drilled because of the cavity in the flexible area. Although the increase in air holes solves the problem of gas expansion and stratification, it also increases the risk of chemicals entering, often causing the flexible area to be contaminated by chemicals. In addition, the production process requires the addition of multiple tape sticking and tearing processes, resulting in a long production process. Summary of the invention

[0003] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art and to provide a method for manufacturing a rigid-flexible board without air holes, which can solve the problem of gas expansion and stratification without using a drilling method.

[0004] The present invention provides a method for manufacturing a rigid-flexible board without air holes, comprising the following steps:

[0005] Lamination: Stacking and laminating several core boards into a motherboard;

[0006] Initial copper reduction: reduce the surface copper thickness of the motherboard;

[0007] Initial drilling: Drill holes on the motherboard that need to be filled with resin according to design requirements;

[0008] Initial copper plating: a layer of copper is plated on the inner wall of the hole that needs to be filled with resin;

[0009] Resin plugging: Fill the holes that need to be filled with resin with resin;

[0010] Post-solder mask baking: low-temperature drying of the motherboard after resin plugging to solidify the resin;

[0011] External light imaging: a layer of dry film is applied to the surface of the hole after the resin plugging to protect the resin;

[0012] Secondary copper reduction: reduce the surface copper thickness of the motherboard again;

[0013] Alkaline etching: removes the dry film applied on the motherboard during the external photo-imaging step;

[0014] Three times copper reduction: reduce the surface copper thickness of the motherboard again;

[0015] Secondary copper plating: a layer of copper is plated on the holes filled with resin;

[0016] Secondary drilling: drilling component holes and / or electrical connection holes on the motherboard;

[0017] Three-time copper plating: a layer of copper is plated on the inner wall of the component hole and / or electrical connection hole;

[0018] Secondary external light imaging: to make the copper pattern on the motherboard surface;

[0019] Copper-tin plating: Selective copper plating of patterns made according to the secondary external light imaging step

[0020] Alkaline etching: Etch the motherboard to make surface copper circuits.

[0021] A method for manufacturing a rigid-flexible board without air holes according to an embodiment of the present invention has at least the following beneficial effects: the resin is solidified by low-temperature solder resist and post-baking, and the gas in the flexible zone cavity will not expand due to heat, thereby avoiding the problem of gas expansion and stratification.

[0022] According to the method for manufacturing a rigid-flexible board without air holes described in the present invention, when the product requires positive etching, a plasma step is also included before the initial copper deposition step. In the plasma step, plasma technology is used to clean and activate the surface of the motherboard to ensure better adhesion of the copper layer.

[0023] According to the method for manufacturing a rigid-flexible board without air holes described in the present invention, low-temperature plasma is used in the plasma step, and a low-temperature recessed etching process is used.

[0024] According to the method for manufacturing a rigid-flexible board without air holes described in the present invention, when the product requires positive etching, a secondary plasma step is also included before the three copper deposition steps. In the secondary plasma step, plasma technology is used to clean and activate the surface of the motherboard to ensure better adhesion of the copper layer.

[0025] According to the method for manufacturing a rigid-flexible board without air holes described in the present invention, low-temperature plasma is used in the secondary plasma step, and a low-temperature recessed etching process is used.

[0026] According to the method for manufacturing a rigid-flexible board without air holes described in the present invention, in the post-solder resist baking step, a low-temperature tunnel furnace is used to bake the motherboard.

[0027] According to the method for manufacturing a rigid-flexible board without air holes described in the present invention, before the external light imaging step, it also includes a primary ceramic grinding step, in which the mother board is polished and the resin on the board surface and the protruding resin are cleaned.

[0028] According to the method for manufacturing a rigid-flexible board without air holes described in the present invention, before the secondary copper deposition step, it also includes a secondary ceramic grinding step. In the secondary ceramic grinding step, the copper on the motherboard surface is ground to make the copper on the motherboard surface flat.

[0029] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention is further described below in conjunction with the accompanying drawings and embodiments;

[0031] Figure 1 The process flow chart of the preferred embodiment of the present invention. DETAILED DESCRIPTION

[0032] This section will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it cannot be understood as a limitation on the scope of protection of the present invention.

[0033] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0034] In the description of the present invention, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed" etc. are understood as not including the number itself, and "above", "below", "within" etc. are understood as including the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0035] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0036] Reference Figure 1 A method for manufacturing a rigid-flexible board without air holes comprises the following steps:

[0037] Lamination: Stacking and laminating several core boards into a motherboard;

[0038] Initial copper reduction: reduce the surface copper thickness of the motherboard;

[0039] Initial drilling: Drill holes on the motherboard that need to be filled with resin according to design requirements;

[0040] Initial copper plating: a layer of copper is plated on the inner wall of the hole that needs to be filled with resin;

[0041] Resin plugging: Fill the holes that need to be filled with resin with resin;

[0042] Post-solder mask baking: low-temperature drying of the motherboard after resin plugging to solidify the resin;

[0043] External light imaging: a layer of dry film is applied to the surface of the hole after the resin plugging to protect the resin;

[0044] Secondary copper reduction: reduce the surface copper thickness of the motherboard again;

[0045] Alkaline etching: removes the dry film applied on the motherboard during the external photo-imaging step;

[0046] Three times copper reduction: reduce the surface copper thickness of the motherboard again;

[0047] Secondary copper plating: a layer of copper is plated on the holes filled with resin;

[0048] Secondary drilling: drilling component holes and / or electrical connection holes on the motherboard;

[0049] Three-time copper plating: a layer of copper is plated on the inner wall of the component hole and / or electrical connection hole;

[0050] Secondary external light imaging: to make the copper pattern on the motherboard surface;

[0051] Copper-tin plating: Selective copper plating of the pattern produced according to the secondary external light imaging step;

[0052] Alkaline etching: Etch the motherboard to make surface copper circuits.

[0053] By curing the resin through low-temperature solder resist post-baking, the gas in the flexible zone cavity will not expand due to heat, so there is no need to punch holes to balance the gas pressure, thus avoiding the problem of gas expansion and stratification. At the same time, there is no need to add multiple tape application and removal processes in the process flow, which improves production efficiency.

[0054] It is worth noting that in the embodiment of the present invention, when the product has a positive etchback requirement, a plasma step is also included before the first copper deposition step. In the plasma step, plasma technology is used to clean and activate the surface of the motherboard to ensure that the copper layer can adhere better. A secondary plasma step is also included before the third copper deposition step. In the secondary plasma step, plasma technology is used to clean and activate the surface of the motherboard to ensure that the copper layer can adhere better.

[0055] Furthermore, in the plasma step, low-temperature plasma is used for fabrication and a low-temperature recessed etching procedure is adopted, and in the secondary plasma step, low-temperature plasma is used for fabrication and a low-temperature recessed etching procedure is adopted.

[0056] It is worth noting that the operating temperature of low-temperature plasma low-temperature etching is 20 to 35 degrees Celsius.

[0057] It is understandable that the low temperature etching process will not cause the gas in the flexible zone cavity to expand due to heat, so there is no need to punch holes to balance the gas pressure, thereby avoiding the problem of gas expansion and stratification. At the same time, there is no need to add multiple tape application and removal processes in the process flow, which improves production efficiency.

[0058] In an embodiment of the present invention, in the solder resist post-baking step, a low-temperature tunnel furnace is used to bake the motherboard.

[0059] By curing the resin through low-temperature solder resist post-baking, the gas in the flexible zone cavity will not expand due to heat, so there is no need to punch holes to balance the gas pressure, thus avoiding the problem of gas expansion and stratification. At the same time, there is no need to add multiple tape application and removal processes in the process flow, which improves production efficiency.

[0060] It should be noted that, in the embodiment of the present invention, the baking temperature of the low-temperature tunnel furnace is 80 to 130 degrees Celsius.

[0061] It is worth noting that, in the embodiment of the present invention, before the external light imaging step, a primary ceramic grinding step is also included, in which the mother board is polished to clean the resin on the board surface and the protruding resin.

[0062] It should be noted that after the solder mask post-baking step, the resin may splash onto the motherboard surface. The ceramic grinding step can grind the motherboard surface to make the motherboard flat as a whole. In the production process, the motherboard surface may have defects such as unevenness, scratches, and protrusions. The ceramic grinding plate can remove these surface defects to ensure that the surface of the final product is smooth and suitable for subsequent electroplating, photolithography and other processing processes.

[0063] It is worth noting that, in the embodiment of the present invention, before the secondary copper deposition step, a secondary ceramic grinding step is also included. In the secondary ceramic grinding step, the copper on the motherboard surface is ground to make the copper on the motherboard surface smooth.

[0064] It is understandable that the ceramic grinding plate can remove oxides, residual oil stains, etc. on the PCB surface or hole wall through fine grinding, improve the surface conductivity, and ensure that the subsequent electroplating or welding process can proceed smoothly.

[0065] The embodiments of the present invention are described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the technical field without departing from the purpose of the present invention.

Claims

1. A method for manufacturing a rigid-flex board without air holes, characterized in that: The following steps are involved: Lamination: Stacking and laminating several core boards into a motherboard; Initial copper reduction: reduce the surface copper thickness of the motherboard; Initial drilling: Drill holes on the motherboard that need to be filled with resin according to design requirements; Initial copper plating: a layer of copper is plated on the inner wall of the hole that needs to be filled with resin; Resin plugging: Fill the holes that need to be filled with resin with resin; Post-solder mask baking: low-temperature drying of the motherboard after resin plugging to solidify the resin; External light imaging: a layer of dry film is applied to the surface of the hole after the resin plugging to protect the resin; Secondary copper reduction: reduce the surface copper thickness of the motherboard again; Alkaline etching: removes the dry film applied on the motherboard during the external photo-imaging step; Three times copper reduction: reduce the surface copper thickness of the motherboard again; Secondary copper plating: a layer of copper is plated on the holes filled with resin; Secondary drilling: drilling component holes and / or electrical connection holes on the motherboard; Three-time copper plating: a layer of copper is plated on the inner wall of the component hole and / or electrical connection hole; Secondary external light imaging: to make the copper pattern on the motherboard surface; Copper-tin plating: Selective copper plating of patterns made according to the secondary external light imaging step Alkaline etching: Etch the motherboard to make surface copper circuits.

2. The method for manufacturing a rigid-flexible board without air holes according to claim 1, characterized in that: When the product requires positive etchback, a plasma step is also included before the initial copper deposition step. In the plasma step, plasma technology is used to clean and activate the surface of the motherboard to ensure better adhesion of the copper layer.

3. The method for manufacturing a rigid-flexible board without air holes according to claim 2, characterized in that: In the plasma step, low-temperature plasma is used and a low-temperature etch-back process is used.

4. The method for manufacturing a rigid-flexible board without air holes according to claim 2, characterized in that: When the product requires positive etchback, a secondary plasma step is included before the three copper deposition steps. In the secondary plasma step, plasma technology is used to clean and activate the surface of the motherboard to ensure better adhesion of the copper layer.

5. The method for manufacturing a rigid-flexible board without air holes according to claim 4, characterized in that: In the secondary plasma step, low temperature plasma is used and a low temperature etch back process is adopted.

6. The method for manufacturing a rigid-flexible board without air holes according to claim 1, characterized in that: In the post-solder mask baking step, a low-temperature tunnel furnace is used to bake the motherboard.

7. The method for manufacturing a rigid-flexible board without air holes according to claim 1, characterized in that: Before the external light imaging step, a primary ceramic grinding step is also included, in which the mother board is polished to clean the resin on the board surface and the protruding resin.

8. The method for manufacturing a rigid-flexible board without air holes according to claim 1, characterized in that: Before the secondary copper deposition step, a secondary ceramic grinding step is also included. In the secondary ceramic grinding step, the copper on the motherboard surface is ground to make the copper on the motherboard surface flat.

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