Method for solving incomplete development of signal stability air hole

Abstract

The invention relates to a method for solving incomplete development of a signal stability air hole. The method comprises the following steps: S100, circuit board preorder processing; s200, air holes are drilled in the circuit board, a dry film is pressed on the circuit board, windows are formed in the positions of the air holes, glue residues in the air holes are removed through plasma, and the dry film is removed; s300, carrying out subsequent processing on the circuit board; after the processing flow of the air hole is moved to the surface treatment of the circuit board, the condition that a wet film and solder resist ink flow into the air hole in the preorder treatment process of the circuit board to cause incomplete development can be avoided, and meanwhile, in the processing process of the air hole, plasma glue residue removal needs to be carried out in the air hole, so that the development efficiency is improved. The plasma has a destructive effect on the solder resist ink, so that a layer of dry film for protecting the solder resist ink is additionally arranged on the circuit board before the glue residue is removed by the plasma, and the ink at a non-air hole can be prevented from being damaged by the plasma.

Description

Technical Field

[0001] The invention relates to the technical field of PCB, and in particular to a method for solving the problem of incomplete development of air holes for signal stability. Background Art

[0002] For existing high-end optical module boards, some air holes (i.e. laser blind holes) are designed on the PCB to strictly control the impedance of the PCB and increase the stability of the PCB signal.

[0003] The existing processing flow of PCB with gold fingers and air holes drilled is: cutting - inner layer graphics - pressing - drilling - copper plating, board electricity - outer layer graphics - drilling air holes - electrical gold fingers - outer layer AOI - solder mask - text - surface treatment - molding - testing - FQC - packaging.

[0004] It can be seen from this that after the air holes are drilled on the circuit board, the wet film and solder mask ink are easy to flow into the air holes, which can easily lead to unclean development and affect the signal and appearance of the product. Summary of the invention

[0005] In view of this, it is necessary to provide a method to solve the problem of incomplete development of signal stability air holes, so as to solve the problem that after drilling air holes on the circuit board, wet film and solder mask ink are easy to flow into the air holes, resulting in unclean development, affecting the signal and appearance of the product.

[0006] The present invention provides a method for solving the problem of incomplete development of air holes in signal stability, comprising the following steps: S100, circuit board pre-processing; S200, drilling air holes on the circuit board, pressing the dry film onto the circuit board and opening windows at the positions of the air holes, removing the glue residue in the air holes with plasma, and removing the dry film; S300: Post-processing of circuit board.

[0007] Further, S110, cutting the material, cutting out the core board, the PP sheet and the outer copper foil according to the size requirements of the product drawing; S120, inner layer pattern, producing an inner layer circuit pattern on the core board; S130, laminating, stacking and fixing the core board, the PP sheet and the outer copper foil, and then pressing them into a production board; S140, drilling, drilling holes at corresponding positions of the production board according to the design data; S150, copper deposition, depositing thin copper with a thickness of 0.3-0.8 um on the surface and in the holes of the production board by chemical deposition; S160, electroplating the production board after copper deposition; S170, outer graphics; S180, electric gold finger; S190, outer layer AOI, optical inspection of outer layer defects of circuit boards; S101, solder mask, after the etched board surface is roughened, a layer of photosensitive ink is printed on its surface. After exposure and development, the ink exposes the PAD and holes that the customer needs to solder; S102, text, forming character graphics on the surface of the PCB to provide information for component installation and future maintenance of the PCB; S103. Surface treatment.

[0008] Furthermore, the electrical gold finger comprises the following steps: S181, pre-treatment, the production plate is polished by sandblasting process, and pickled without grinding and brushing; S182, primary auxiliary electro-gold wet film; S183, auxiliary image transfer, exposing and developing the wet film to reveal the finger positions to be gold plated; S184, primary auxiliary electroplating gold dry film; S185, auxiliary image transfer, exposing and developing the dry film to reveal the finger positions to be gold plated; S186, gold-plated fingers; S187, film removal; S188, pre-treatment, the production plate is polished by sandblasting process, and pickled without grinding and brushing; S189, secondary auxiliary etching of lead wet film; S1810, auxiliary image transfer, exposing and developing the wet film to reveal the lead position to be etched; S1811, secondary auxiliary etching of lead dry film; S1812, auxiliary image transfer, exposing and developing the dry film to reveal the lead positions to be etched; S1813, alkaline etching, etching away the leads of the gold fingers; S1814, film removal.

[0009] Furthermore, the post-processing of the circuit board includes the following steps: S310, molding, using CNC gong machine to cut the large plate into the size required by the customer; S320, test, apply current to one end of a network to be tested, measure at the other end of the network, and judge whether the network (wire) is conductive, the resistance is large or disconnected according to the change of current value, to ensure that the electrical performance of the PCB meets the requirements; S330, FQC, inspect the appearance of finished PCB boards according to customer acceptance standards and our inspection standards. If there are any defects, repair them in time to ensure excellent quality control for customers; S340, packaging, the finished PCB boards that have passed the inspection are packaged using vacuum packaging film under heating and vacuum conditions to prevent the finished PCB boards from getting damp and to facilitate storage and transportation.

[0010] Furthermore, in step S200, the diameter of the air hole is not less than 0.12 mm, and the depth of the air hole cannot exceed 0.6 mm.

[0011] Further, in step S200, the air holes are realized by double-sided laser drilling.

[0012] Furthermore, in steps S182 and S189, the primary auxiliary electro-gold wet film and the secondary auxiliary etching lead wet film both use wet films of model Sun EB02.

[0013] Further, in step S186, the thickness of the gold layer of the gold-plated finger is not less than 30u", and the thickness of the nickel layer is not less than 200u".

[0014] Furthermore, in step S103, the surface treatment includes gold finger sealing and nickel-gold immersion.

[0015] Furthermore, sealing the gold finger includes sticking red tape on the gold finger, and during the nickel-gold deposition process, the thickness of the gold layer is not less than 2u", and the thickness of the nickel layer is not less than 200u".

[0016] Compared with the prior art, by moving the processing flow of the air holes to after the surface treatment of the circuit board, it is possible to avoid the wet film and solder resist ink in the previous processing of the circuit board from flowing into the air holes, resulting in incomplete development. At the same time, in the process of processing the air holes, since plasma desmearing is required in the air holes, plasma has a destructive effect on the solder resist ink. Therefore, before plasma desmearing, a layer of dry film for protecting the solder resist ink is added to the circuit board to avoid the ink in non-air holes from being damaged by plasma. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A flow chart of a method for solving the problem of incomplete air hole development in signal stability provided by an embodiment of the present invention; Figure 2 A schematic diagram of ink remaining in the air of a circuit board in a conventional production method; Figure 3 A cross-sectional view of the air hole of a circuit board after adopting the method for solving the problem of incomplete development of the air hole for signal stability provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0019] like Figure 1 As shown, the present invention provides a method for solving the problem of incomplete development of air holes in signal stability, comprising: Step S100: pre-processing of the circuit board.

[0020] Step S200, drilling air holes on the circuit board, pressing the dry film onto the circuit board and opening windows at the positions of the air holes, removing the glue residue in the air holes with plasma, and removing the dry film.

[0021] Step S300: Post-processing of the circuit board.

[0022] During implementation, by moving the processing flow of the air holes to after the circuit board surface treatment, it is possible to avoid the wet film and solder resist ink in the previous processing of the circuit board from flowing into the air holes, resulting in incomplete development. At the same time, in the process of processing the air holes, since plasma desmearing is required in the air holes, plasma has a destructive effect on the solder resist ink. Therefore, before plasma desmearing, a layer of dry film for protecting the solder resist ink is added to the circuit board to avoid the ink in non-air holes from being damaged by plasma.

[0023] In step S100, the circuit board pre-processing includes the following steps: S110, cutting materials, cutting out core board, PP sheet and outer copper foil according to the size requirements of product drawings. The core board is Shengyi SY-S7439G.

[0024] S120, inner layer pattern, inner layer circuit pattern is produced on the core board, using wet film process, and the wet film thickness is controlled to be 10-12um.

[0025] S130, lamination, the core board, PP sheet and outer copper foil are stacked and fixed, and then pressed into a production board. In this embodiment, L1-L6 are pressed into a production board (taking a 6-layer board as an example). Among them, the thickness of the pressed production board is 1.5±0.075mm. After pressing, the board thickness needs to be tested to ensure that the board thickness meets the above requirements. The pressed board needs to be processed by XR shooting, cutting and grinding in sequence, and a ceramic brush can be used for grinding.

[0026] S140, drilling, drilling holes at corresponding positions of the production board according to the design data. It should be noted that the holes drilled in this step are non-air holes.

[0027] S150, copper deposition, depositing thin copper with a thickness of 0.3-0.8 um on the surface of the production board and in the holes by chemical deposition. Before copper deposition, a plasma process is required to remove the slag in the holes drilled in step S140.

[0028] S160, electroplating the production board after copper deposition. This step is a prior art and will not be described in detail in the present invention.

[0029] S170, outer layer graphics, using negative film process, outer layer dry film using Hongrui HL-1140 20inch*600ft, thickness 38.00±2um.

[0030] S180, electric gold finger; In step S180, the process of electro-gold finger is as follows: S181, pre-treatment, the production plate is polished by sandblasting process, and pickled without grinding and brushing; S182, one-time auxiliary electro-gold wet film, printing anti-electro-gold wet film on the circuit board, wherein the model of the wet film is Sun EB02; S183, auxiliary image transfer, exposing and developing the wet film to reveal the finger positions to be gold plated; S184, a primary auxiliary electro-gold dry film, covering a layer of electro-resistant gold dry film on the circuit board; S185, auxiliary image transfer, exposing and developing the dry film to reveal the finger positions to be gold plated; S186, gold-plated fingers, gold layer thickness not less than 30u", nickel layer thickness not less than 200u"; S187, film stripping, using film stripping solution to strip the primary auxiliary electroplating gold wet film and the primary auxiliary electroplating gold dry film; S188, pre-treatment, the production plate is polished by sandblasting process, and pickled without grinding and brushing; S189, secondary auxiliary etching lead wet film, printing wet film on the circuit board, wherein the model of the wet film is Sun EB02; S1810, auxiliary image transfer, exposing and developing the wet film to reveal the lead position to be etched; S1811, secondary auxiliary etching of lead dry film, covering a layer of dry film on the circuit board; S1812, auxiliary image transfer, exposing and developing the dry film to reveal the lead positions to be etched; S1813, alkaline etching, etching away the leads of the gold fingers; S1814, film stripping, using film stripping solution to strip the secondary auxiliary etching lead wet film and the secondary auxiliary etching lead dry film.

[0031] In step S180, since it is difficult to ensure the fit between the dry film and the circuit board, the electric gold finger adopts the wet film + dry film method to obtain a high probability of a good circuit board, and the test data is as follows.

[0032] Table 1 - Yield test table

[0033] Statistical anomalies include: dry film / wet film scratches and permeation.

[0034] S190, outer layer AOI, optical inspection of outer layer defects of circuit boards, repair or scrapping of defective boards; S101, solder mask, after the etched board surface is roughened, a layer of photosensitive ink is printed on its surface. After exposure and development, the ink exposes the PAD and holes that the customer needs to solder; S102, text, forming character graphics on the surface of the PCB to provide information for component installation and future maintenance of the PCB; In steps S101-S102, a solder mask layer and text are formed on the surface of the production board after development and etching. In some specific embodiments of the present invention, the step of forming a solder mask layer and text on the surface of the production board after development and etching includes: sequentially performing solder mask pre-treatment, silk-screen solder mask ink, pre-baking, exposure, and development on the surface of the production board after development and etching, and after the solder mask ink is developed, characters are printed on the corresponding positions of the board surface according to customer needs, and then post-baking to form the solder mask layer and text.

[0035] S103, surface treatment, including sealing gold fingers and nickel-gold immersion, wherein the sealing gold fingers includes sticking red tape on the gold fingers, and during the nickel-gold immersion process, the thickness of the gold layer is not less than 2u", and the thickness of the nickel layer is not less than 200u".

[0036] After the surface treatment of the circuit board is completed, the process of step S200 is performed to complete the processing of the air holes.

[0037] In step S200, when drilling the air hole, the diameter of the air hole is not less than 0.12 mm, and the depth of the air hole cannot exceed 0.6 mm, which is achieved by double-sided laser drilling.

[0038] Since in step S200, after the laser air hole is drilled, there is carbonization in the air hole (the high temperature of laser drilling carbonizes the resin in the substrate and produces glue residue), it is easy to cause a short circuit in the subsequent welding process. For this reason, this embodiment performs plasma treatment on the air hole to remove the above-mentioned glue residue. However, plasma has a destructive effect on solder resist ink, so before plasma removal of glue residue, a layer of dry film for protecting solder resist ink is added to the circuit board to prevent the ink in non-air holes from being damaged by plasma. Among them, the plasma degumming time is 45 minutes.

[0039] In step S300, the circuit board post-processing includes the following steps: S310, molding, using CNC gong machine to cut the large plate into the size required by the customer.

[0040] S320, test, apply current to one end of a network to be tested, measure at the other end of the network, and judge whether the network (wire) is conductive, the resistance is large or disconnected according to the change of current value, to ensure that the electrical performance of the PCB meets the requirements; S330, FQC, inspect the appearance of finished PCB boards according to customer acceptance standards and our inspection standards. If there are any defects, repair them in time to ensure excellent quality control for customers; S340, packaging, the finished PCB boards that have passed the inspection are packaged using vacuum packaging film under heating and vacuum conditions to prevent the finished PCB boards from getting damp and to facilitate storage and transportation.

[0041] like Figure 2 As shown in the figure, in the traditional process, after the air holes are drilled on the circuit board, the wet film and solder resist ink easily flow into the air holes, that is, the part inside the holes in the figure, so that the development is not clean, affecting the signal and appearance of the product. After processing the air holes by this method, the problem of incomplete development of the air holes for signal stability can be effectively solved. Figure 3 The figure shows a slice of an air hole, from which it can be seen that there is no ink in the hole.

[0042] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for solving the problem of incomplete development of air holes in signal stability, characterized in that: The following steps are involved: S100, circuit board pre-processing; S200, drilling air holes on the circuit board, pressing the dry film onto the circuit board and opening windows at the positions of the air holes, removing the glue residue in the air holes with plasma, and removing the dry film; S300: Post-processing of circuit board.

2. The method for solving the problem of incomplete development of air holes in signal stability according to claim 1, characterized in that: The circuit board pre-processing comprises the following steps: S110, cutting materials, cutting out core board, PP sheet and outer copper foil according to the size requirements of product drawings; S120, inner layer pattern, producing an inner layer circuit pattern on the core board; S130, laminating, stacking and fixing the core board, the PP sheet and the outer copper foil, and then pressing them into a production board; S140, drilling, drilling holes at corresponding positions of the production board according to the design data; S150, copper deposition, depositing thin copper with a thickness of 0.3-0.8 um on the surface and in the holes of the production board by chemical deposition; S160, electroplating the production board after copper deposition; S170, outer graphics; S180, electric gold finger; S190, outer layer AOI, optical inspection of outer layer defects of circuit boards; S101, solder mask, after the etched board surface is roughened, a layer of photosensitive ink is printed on its surface. After exposure and development, the ink exposes the PAD and holes that the customer needs to solder; S102, text, forming character graphics on the surface of the PCB to provide information for component installation and future maintenance of the PCB; S103. Surface treatment.

3. The method for solving the problem of incomplete development of air holes in signal stability according to claim 2, characterized in that: The electrical gold finger comprises the following steps: S181, pre-treatment, the production plate is polished by sandblasting process, and pickled without grinding and brushing; S182, one-time auxiliary electro-gold wet film; S183, auxiliary image transfer, exposing and developing the wet film to reveal the finger positions to be gold plated; S184, primary auxiliary electroplating gold dry film; S185, auxiliary image transfer, exposing and developing the dry film to reveal the finger positions to be gold plated; S186, gold-plated fingers; S187, film removal; S188, pre-treatment, the production plate is polished by sandblasting process, and pickled without grinding and brushing; S189, secondary auxiliary etching of lead wet film; S1810, auxiliary image transfer, exposing and developing the wet film to reveal the lead position to be etched; S1811, secondary auxiliary etching of lead dry film; S1812, auxiliary image transfer, exposing and developing the dry film to reveal the lead positions to be etched; S1813, alkaline etching, etching away the leads of the gold fingers; S1814, film removal.

4. The method for solving the problem of incomplete development of air holes in signal stability according to claim 1, characterized in that: The post-processing of the circuit board includes the following steps: S310, molding, using CNC gong machine to cut the large plate into the size required by the customer; S320, test, apply current to one end of a network to be tested, measure at the other end of the network, and judge whether the network is turned on, the resistance value or whether it is disconnected according to the change value of the current to ensure that the electrical performance of the PCB meets the requirements; S330, FQC, inspect the appearance of finished PCB boards according to customer acceptance standards and our inspection standards. If there are any defects, repair them in time to ensure excellent quality control for customers; S340, packaging, the finished PCB boards that have passed the inspection are packaged using vacuum packaging film under heating and vacuum conditions to prevent the finished PCB boards from getting damp and to facilitate storage and transportation.

5. The method for solving the problem of incomplete development of air holes in signal stability according to claim 1, characterized in that: In step S200, the diameter of the air hole is not less than 0.12 mm, and the depth of the air hole cannot exceed 0.6 mm.

6. The method for solving the problem of incomplete development of air holes in signal stability according to claim 1, characterized in that: In step S200, the air holes are formed by double-sided laser drilling.

7. The method for solving the problem of incomplete development of air holes in signal stability according to claim 3, characterized in that: In steps S182 and S189, the primary auxiliary electro-gold wet film and the secondary auxiliary etching lead wet film both use wet films of model Sun EB02.

8. The method for solving the problem of incomplete development of air holes in signal stability according to claim 3, characterized in that: In step S186, the thickness of the gold layer of the gold-plated finger is not less than 30u", and the thickness of the nickel layer is not less than 200u".

9. The method for solving the problem of incomplete development of air holes in signal stability according to claim 2, characterized in that: In step S103, the surface treatment includes gold finger sealing and nickel-gold immersion.

10. The method for solving the problem of incomplete development of air holes in signal stability according to claim 9, characterized in that: Sealing the gold finger includes sticking red tape on the gold finger. During the nickel-gold immersion process, the thickness of the gold layer shall not be less than 2u", and the thickness of the nickel layer shall not be less than 200u".

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