Methods to improve PCB metallization half hole flash

Abstract

The invention discloses a method for improving the flash of PCB metallized half hole, which relates to the technical field of printed circuit board production, including the steps of pre-drilling, copper deposition, pattern electroplating, etching without tin stripping, positive and negative drilling, tin stripping and drilling half holes, etc., pre-drilling a circular hole before copper deposition so that the inner wall of the metallized half hole has a deposited copper layer, and then performing positive and negative drilling and drilling half holes after etching is completed, so as to avoid the tin surface being scratched during the drilling process and then the copper layer of the circuit part being eroded during etching to cause defective products. Positive and negative drilling means drilling the metallized half hole in clockwise and counterclockwise directions in turn, and then drilling the half hole so that the metallized half hole is finally formed, which can avoid the gong cutter pulling the copper layer to produce flash during the drilling process, and improve product quality and yield rate.

Description

Technical Field

[0001] The invention relates to the technical field of printed circuit board production, in particular to a method for improving the flashing of a metallized half hole of a PCB. Background Art

[0002] In the production of printed circuit boards (PCBs), metallized half holes can not only realize the conduction function of round holes, but also use the hole walls of the half holes for welding and fixation to achieve the fixation of chip pins. This is a common design in the production of printed circuit boards.

[0003] The current PCB metallized half-hole production process is roughly as follows: substrate drilling - copper plating - pattern plating - film stripping - half-hole drilling - PCB alkaline etching - tin stripping - solder masking, etc. During the mechanical processing of the half-hole drilling, the tin surface is easily scratched, resulting in the etching solution eroding the outer layer of the half-hole through the cutting area during the etching process, thereby reducing the half-hole welding contact surface and causing defective products. On the other hand, during the drilling of the half-hole, there is no plate support on the cutting path. Under the squeezing and pulling of the blade on the drilling cutter, the metal burrs that bend inward or cannot be cut will be generated, resulting in waste products. Summary of the invention

[0004] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art, and the technical solution adopted is:

[0005] The present invention provides a method for improving PCB metallization half hole flashing, comprising the following steps:

[0006] Pre-drilling: Use a drill bit to drill a circular hole at a preset position;

[0007] Copper deposition: Through the chemical copper deposition process, a copper layer is deposited on the surface of the circuit board and the inner wall of the circular hole;

[0008] Graphic electroplating: After copper deposition, the copper layer surface of the circuit part is pre-plated with a tin protective layer to ensure that the copper layer of the circuit part is exposed during etching;

[0009] Etching without tin stripping: The parts outside the circuit are corroded, leaving the uncorroded parts as the circuit pattern. After etching, the tin stripping process is not performed to avoid the generation of flash in subsequent cutting processing;

[0010] Forward and reverse drilling: After etching is completed, forward drilling and reverse drilling are carried out in sequence, and the edge of the circular hole is drilled with a drill bit;

[0011] Tin stripping: After completing the front and back drilling, remove the etched protective layer of the circuit to expose the circuit part;

[0012] Gong half hole: After de-tinning, the gong knife gongs the outer contour of the circuit board to form the metallized half hole.

[0013] Furthermore, in the steps of forward drilling and reverse drilling, the drill bit drills the circular hole in a clockwise and counterclockwise direction respectively.

[0014] Furthermore, when performing the forward drilling and reverse drilling steps, the tangent direction of the outer edge of the rotating area of ​​the drill bit is toward the center of the circular hole.

[0015] Furthermore, in the steps of forward drilling and reverse drilling, the drill bit penetrates into the circular hole to a depth of 2 mil in the axial direction.

[0016] Furthermore, the forward and reverse drilling steps and the half-hole drilling steps need to be carried out in conjunction with the dust removal step to reduce dust during the cutting process.

[0017] Furthermore, the method includes a solder resist step, in which a solder resist layer is formed on the surface of the board other than the preset soldering positions on the circuit board.

[0018] The method for improving the flash of the metallized half hole of PCB described in the present invention has at least the following beneficial effects: the method for improving the flash of the metallized half hole of PCB in the embodiment of the present invention comprises the steps of pre-drilling, copper deposition, pattern electroplating, etching without tin stripping, positive and negative drilling, tin stripping and drilling half holes, etc., pre-drilling a circular hole before copper deposition so that the inner wall of the metallized half hole has a deposited copper layer, and then performing positive and negative drilling and drilling half holes and other drilling processes after etching is completed, so as to avoid scratching the tin surface during the drilling process and then eroding the copper layer of the circuit part during etching to cause defective products. Positive and negative drilling means drilling the metallized half hole in clockwise and counterclockwise directions in turn, and pre-cutting a part of the copper layer. After the positive and negative drilling is completed, the tin is stripped, and the copper layer is protected by the tin surface to avoid the flash of the copper layer during the positive and negative drilling process. After the positive and negative drilling is completed, the half hole is drilled to finally form the metallized half hole, which can avoid the flash caused by the gong cutter pulling the copper layer during the drilling of the half hole, thereby improving the product quality and yield rate.

[0019] 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

[0020] The present invention is further described below in conjunction with the accompanying drawings and embodiments;

[0021] Figure 1 A process schematic diagram of a method for improving PCB metallization half-hole flashing according to an embodiment of the present invention;

[0022] Figure 2 A schematic diagram of the forward and reverse drilling and drilling half-hole steps of the method for improving the flash of PCB metallization half-hole according to an embodiment of the present invention;

[0023] Figure 3 A schematic diagram of a metallized half hole according to a method for improving PCB metallized half hole flashing according to an embodiment of the present invention.

[0024] Reference numerals:

[0025] Circuit board 10; circuit 11; round hole 12; positive drilling position 13; reverse drilling position 14; gong plate tool path 15; metallized half hole 16. DETAILED DESCRIPTION

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] Reference Figure 1 , an embodiment of the present invention provides a method for improving PCB metallization half hole flashing, comprising the following steps:

[0031] Step S100 pre-drilling: cutting the circuit board 10, drilling a circular hole 12 on the circuit board 10, and the circular hole 12 serves as a blank hole for the metallized half hole 16; it also includes processes such as baking the plate, inner layer circuit 11, inner layer etching, and pressing, and finally obtaining a circuit board 10 to be processed with an outer shape line, using a drill bit to drill a circular hole 12 at a preset position on the circuit board 10, and the circular hole 12 is formed at one time by the drill bit, which is efficient and convenient for depositing a copper layer on the hole wall in the subsequent steps.

[0032] Step S200 copper deposition: a copper layer is deposited on the surface of the hole wall of the circular hole 12 by a chemical copper deposition process; a uniform conductive layer is deposited on the hole wall by an oxidation-reduction reaction, and then the copper is thickened by electroplating to form a conductive circuit.

[0033] Step S300 Graphic electroplating: Use graphic electroplating method to process the outer layer circuit, that is, first pre-plate a layer of lead-tin anti-corrosion layer on the graphic part of the circuit, and expose the copper layer of the circuit part during etching.

[0034] Step S400: Etching without tin stripping: After completing the pattern electroplating step, use etching solution to corrode the parts outside the circuit, leaving the uncorroded part as the circuit pattern. The surface of the circuit pattern part is covered with a layer of tin protective layer. After the etching is completed, the tin stripping treatment is not performed. It is used to protect the copper layer through the tin surface and avoid the formation of metal flash caused by the drill bit cutting the copper layer during the forward and reverse drilling processes.

[0035] Step S500: forward and reverse drilling: after the etching step is completed, forward drilling and reverse drilling are performed, and the edge of the circular hole 12 is drilled using a drill bit. Further, the drill bit drills the circular hole 12 clockwise and counterclockwise respectively, and the forward drilling and reverse drilling respectively drill the edges of different positions on the circular hole 12. Figure 2 , the positive drilling position 13 is the processing position in the positive drilling step, and the drill is used to drill in the positive drilling position 13; the reverse drilling position 14 is the processing position in the reverse drilling step, and the drill is used to drill in the reverse drilling position 14. Optionally, since the direction of metal flash during drilling follows the direction of drill rotation, the tangent direction of the outer edge of the rotating area of ​​the drill is toward the center of the circular hole 12, which helps to reduce the adhesion between the copper layer flash and the cut surface of the circuit board 10 during drilling, and make the incision complete, thereby improving the surface quality of the product. Optionally, the same drill is used in the positive drilling step and the reverse drilling step to reduce equipment investment and tool change time, thereby improving production efficiency. Furthermore, in the steps of positive drilling and reverse drilling, the drill penetrates 2 mils into the axial direction of the circular hole 12, and is only used to cut off the copper layer at a depth of 2 mils, so that the drill cutter does not contact the copper layer in the subsequent half-hole drilling process, thereby avoiding the generation of metal flash again, and not drilling too much of the circuit board 10, thereby reducing processing time and improving efficiency. At the same time, the drilling process is completed in one step, which helps to improve efficiency.

[0036] Step S600: After completing the forward and reverse drilling steps, use a tin stripping agent to remove the protective layer of the circuit that has been etched to expose the circuit part, which is beneficial to the subsequent production of solder mask and other processes.

[0037] Step S700: After the desoldering step is completed, the gong cutter gongs the outer contour of the circuit board 10 to form the metallized half hole 16. Figure 2, the gong plate tool path 15 is the cutting path of the gong cutter in the gong half hole step. The gong plate tool path 15 passes through the edges of the positive drilling position 13 and the reverse drilling position 14. At the same time, the gong cutter cuts the circuit board 10 to form an independent plate, and cuts the circular hole 12 with the deposited copper layer to finally form the metallized half hole 16. At the same time, in the gong half hole step, the gong cutter does not contact the copper layer when cutting the metallized half hole 16 toward the center of the hole, so as to avoid the gong cutter tearing the copper layer at the edge of the metallized half hole 16 during the cutting process and causing a flash.

[0038] Furthermore, the method also includes a solder resist step, wherein the preset welding parts are staggered through the solder resist process to form a solder resist layer on the surface of the plate. A solder resist ink is applied on the circuit board. The solder resist ink is an insulating material, which is printed on the circuit board plate to form a solder resist layer, and plays the role of insulation and preventing welding in the printed circuit board. The solder resist layer is formed by a permanent polymer solder resist coating material, and the solder resist layer covers most of the printed circuit, leaving only the pads for parts welding, electrical performance testing and circuit board plugging exposed.

[0039] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0040] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for improving the flash of a half-hole metallization of a PCB, characterized in that: The following steps are involved: Pre-drilling: Use a drill bit to drill round holes at preset positions on the circuit board; Copper deposition: a copper layer is deposited on the surface of the circuit board and the inner wall of the circular hole through a chemical copper deposition process; Graphic electroplating: After copper deposition, the copper layer surface of the circuit part is pre-plated with a tin protective layer to ensure that the copper layer of the circuit part is exposed during etching; Etching without tin stripping: the parts other than the circuit are etched away, leaving the unetched parts as the pattern of the circuit. After etching, no tin stripping is performed to avoid the generation of flash in subsequent cutting processing; Forward and reverse drilling: After etching is completed, forward drilling and reverse drilling are performed in sequence, and the edge of the circular hole is drilled with a drill bit. The drill bit drills the circular hole clockwise and counterclockwise respectively, and the tangent direction of the outer edge of the rotating area of ​​the drill bit faces the center of the circular hole to avoid contact with the copper layer in subsequent cutting processing to produce flash, and the drill bit penetrates into the axial direction of the circular hole to a depth of 2 mil, and is only used to remove the copper layer with a depth of 2 mil; Tin stripping: After completing the front and back drilling, remove the protective layer of the circuit that has been etched to expose the circuit part; Gong half hole: After de-tinning, use a gong knife to gong the outer contour of the circuit board to form a metallized half hole.

2. The method for improving PCB metallization half hole flashing according to claim 1, characterized in that: The forward and reverse drilling steps and the half-hole drilling step need to be carried out in conjunction with a dust removal step to reduce dust during the cutting process.

3. The method for improving PCB metallization half hole flashing according to claim 1, characterized in that: The step of solder resist is also included, wherein the solder resist is to form a solder resist layer on the surface of the board other than the preset soldering positions on the circuit board.

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