Method for preventing deformation of PCB PAD

Abstract

The invention discloses a method for preventing deformation of a PAD of a PCB, which effectively avoids the deformation problem of the PAD caused by thermal stress in the heating process through the steps of windowing point marking, cap removing, solder mask windowing and the like, not only improves the manufacturing quality of the PCB, but also reduces the rate of defective products caused by deformation of the PAD during solder mask windowing, and further saves the production cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of PCB production, and particularly relates to a method for preventing deformation of a PCB pad. BACKGROUND

[0002] A PCB circuit board is a support body of electronic components and a carrier for electrical connection of electronic components. Precise and complex circuits are integrated on the PCB circuit board. A pad is a device solder pad on the surface of the PCB circuit board. The pad is a key part of the PCB circuit board, and the quality of the pad directly affects the performance and reliability of electronic products. In actual production, the pad is prone to deformation due to various factors, thereby affecting the welding quality and causing an increase in product failure rate. For example, when making a solder mask window, the PCB board needs to be coated with a solder mask ink on the surface. The solder mask window is formed by removing the solder mask ink at a position where the window is needed. Usually, the position where the pad is connected to the circuit connection line needs to be opened. However, the solder mask ink needs to be heated by light to be solidified. When the pad is heated, thermal stress may be generated due to irregular shape of the pad, thereby causing deformation of the pad and resulting in scrap of the PCB board, and increasing production cost. Therefore, a method for preventing deformation of the pad is needed to solve the above problems. SUMMARY

[0003] In view of the above-mentioned technical problems that the pad is prone to deformation after being heated, the present application provides a method for preventing deformation of a PCB pad.

[0004] To achieve the above-mentioned purpose, the present application provides a method for preventing deformation of a PCB pad, comprising the following steps: Marking a window point: obtaining a PCB board, marking a window point on a pad of the PCB board in advance after an etching step is completed, and generating a pre-window marking point; Removing a cap: based on the pre-window marking point, shortening a length of the pad to be less than a length of a window at a connection position of the pad and a circuit connection line; Solder mask windowing: removing solder mask ink on the window at the connection position of the pad and the circuit connection line on the PCB board by a cleaning agent to leak out an inner copper layer, and generating a finished product pad.

[0005] As an improved scheme of the present application, in the step of removing the cap, the length of the pad is shortened to be less than 0.25 mil of the window at the connection position of the pad and the circuit connection line.

[0006] As an improved scheme of the present application, the method for generating the window at the connection position of the pad and the circuit connection line comprises the following steps: Designing sizes of the pad and the circuit connection line window, and generating corresponding pre-window marking points on a film. The pre-windowing mark points are generated on the PCB board through a dry film, an exposure and a developing step; Finally, the anti-soldering ink on the pre-windowing mark points is removed to generate a PAD connection line window of a corresponding size.

[0007] As an improved scheme of the present application, the method for removing the anti-soldering ink on the pre-windowing mark points comprises the following steps: First, a layer of liquid photosensitive anti-soldering ink is coated on the surface of the PCB; According to the windowing size of the connection between the PAD and the circuit connection line designed, a high-power lighting device is used to accurately expose the area needing to be windowed so as to solidify the anti-soldering ink of the area; The anti-soldering ink not exposed is removed to complete the windowing.

[0008] As an improved scheme of the present application, the high-power lighting device is a UV laser.

[0009] As an improved scheme of the present application, the cleaning agent is a developing solution.

[0010] The present application has the following beneficial effects: compared with the prior art, the method for preventing the deformation of the PCB PAD provided by the present application effectively avoids the deformation of the PAD caused by thermal stress in the heating process through the steps of marking the windowing points, removing the caps and anti-soldering windowing, thereby improving the manufacturing quality of the PCB, reducing the defective rate caused by the deformation of the PAD in the anti-soldering windowing, and saving the production cost. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 The present application is a process flow chart. DETAILED DESCRIPTION

[0012] In order to more clearly illustrate the present application, the present application is further described below in combination with the drawings.

[0013] In the following description, the example details are given so as to provide a more in-depth understanding of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. It should be understood that the specific embodiments are only used to explain the present application, and are not used to limit the present application.

[0014] It should be understood that when the terms "comprise" and / or "include" are used in the present specification, it means that there is the described feature, whole, step, operation, element or component, but does not exclude the presence or addition of one or more other features, whole, step, operation, element, component or their combinations.

[0015] Please refer to Figure 1The application discloses a method for preventing deformation of a PCB (Printed Circuit Board) pad. Marking a windowing point: obtaining a PCB, marking a windowing point on a pad of the PCB in advance after an etching step is completed, and generating a pre-windowing mark point; Removing a cap: shortening a length of the pad to be less than a length of the pad and a circuit connection line connection window based on the pre-windowing mark point; Anti-solder windowing: removing anti-solder ink on the pad and the circuit connection line window on the PCB by chemical removal to leak out an inner copper skin, and generating a finished product pad.

[0016] In the marking of the windowing point step, high-precision marking equipment needs to be used to ensure that the position of the pre-windowing mark point is accurate, and the error range should be controlled within a very small range to ensure the accuracy of subsequent processing.

[0017] In the cap removing step, when the length of the pad and the circuit connection line connection is long, the connection line is thinner than the pad during the anti-solder windowing, and the thermal expansion and contraction characteristics of the connection line are different from those of the pad, so that when the anti-solder ink is added and solidified, thermal stress is concentrated on the pad, thereby causing deformation of the pad. Shortening the length of the pad to be less than the length of the pad and the circuit connection line connection window can improve the thermal expansion of the pad, and the thermal stress is uniformly dispersed, so that the problem of deformation of the pad can be effectively avoided.

[0018] In the anti-solder windowing step, the anti-solder ink on the PCB needs to be removed by using a specific cleaning agent, and the concentration and action time of the chemical agent need to be accurately controlled. If the concentration is too high or the action time is too long, the inner copper skin may be corroded, and the conductivity of the pad is affected. If the concentration is too low or the action time is too short, the anti-solder ink cannot be completely removed, and the windowing is not complete.

[0019] The method for removing the anti-solder ink on the pre-windowing mark point needs to ensure uniform coating, no bubbles and impurities when the liquid photosensitive anti-solder ink is coated. When high-power illumination equipment is used for accurate exposure, the exposure time and intensity need to be reasonably adjusted according to the characteristics of the ink and the windowing size. When removing the unexposed anti-solder ink, a suitable cleaning method and equipment need to be used to ensure that the cleaning is clean and no ink is left.

[0020] When an ultraviolet (UV) laser is used as the high-power illumination equipment, the laser needs to be regularly maintained and calibrated to ensure the stability of the output power and the beam quality, so as to ensure the reliability of the exposure effect.

[0021] In the cap removing step in the embodiment, the pad is shortened to be less than 0.25 mil of the pad connection line windowing.

[0022] In the embodiment, the method for generating the windowing at the connection between the PAD and the circuit connection line comprises the following steps: Design the size of the windowing of the PAD and the circuit connection line, and generate the corresponding pre-windowing mark points on the film; Generate the pre-windowing mark points on the PCB through the dry film, exposure and development steps; Finally, remove the solder resist ink on the pre-windowing mark points to generate the corresponding size of the windowing of the PAD connection line.

[0023] When designing the windowing size, the overall layout and electrical performance requirements of the PCB should be fully considered to ensure that the windowing size can meet the welding requirements and will not interfere with the surrounding circuit. When generating the pre-windowing mark points on the film, the accuracy of the mark points should be ensured in advance, and then the windowing precision can be ensured when the solder resist windowing is performed.

[0024] In the embodiment, the method for removing the solder resist ink on the pre-windowing mark points comprises the following steps: First, coat a layer of liquid photosensitive solder resist ink on the surface of the PCB; According to the designed windowing size at the connection between the PAD and the circuit connection line, accurately expose the area that needs to be windowed through the high-power lighting device to solidify the solder resist ink in the area; Remove the unexposed solder resist ink to complete the windowing.

[0025] When the solder resist windowing is performed, the solder resist ink should be coated on the PCB, and then the high-precision and high-power lighting device is used to solidify the PAD and the circuit connection line connection and other parts that need to be windowed. After the solder resist ink is solidified, the residual unexposed solder resist ink is removed through the developing solution to finally complete the windowing at the required position.

[0026] In the embodiment, the high-power lighting device is an ultraviolet (UV) laser. The ultraviolet (UV) laser has the characteristics of high precision and high energy, and can accurately irradiate the area that needs to be windowed to rapidly solidify the solder resist ink in the area. In addition, the light beam quality of the ultraviolet (UV) laser is good, and the energy is uniformly distributed, which can effectively avoid the problem of inconsistent ink solidification caused by uneven energy, thereby ensuring the quality and precision of the windowing.

[0027] In the embodiment, the cleaning agent is a developing solution which can chemically react with the unexposed solder resist ink, dissolve and remove it. When selecting the developing solution, its compatibility with the solder resist ink should be considered to ensure that the unexposed ink can be completely removed without damaging the exposed ink and other parts of the PCB. When using the developing solution for cleaning, the temperature, concentration and action time of the developing solution should be controlled. Too high temperature or too large concentration may accelerate the developing process, but also may cause over-developing and corrode the inner copper; too short action time may not completely remove the unexposed ink. Therefore, the best developing conditions should be determined through experiments to ensure the cleaning effect and the quality of the PCB.

[0028] In the embodiment, The present application has the advantages of: 1. By marking the windowing point, removing the cap and solder resist windowing, the deformation problem caused by thermal stress during heating of the PAD is effectively avoided, not only the manufacturing quality of the PCB is improved, but also the defective rate caused by the deformation of the PAD during the solder resist windowing is reduced, thereby saving the production cost.

[0029] The above only discloses several specific embodiments of the present application, but the present application is not limited thereto, and any changes that can be thought of by those skilled in the art should fall within the protection scope of the present application.

Claims

1. A method for preventing deformation of PADs on a PCB board, characterized in that, Includes the following steps: Marking window opening points: After the etching process is completed, the PCB board is obtained, and window opening points are marked on the PAD of the PCB board in advance to generate pre-window opening marking points; Remove the cap: Based on the pre-opening window mark, shorten the length of the PAD to be less than the length of the window at the connection between the PAD and the circuit connection line; Solder resist opening: On the PCB board, the solder resist ink on the opening corresponding to the connection line between the PAD and the circuit is removed by a cleaning agent to expose the inner copper layer and generate the finished PAD.

2. The method for preventing PCB board PAD deformation according to claim 1, characterized in that, In the cap removal step, the PAD is shortened to be 0.25 mil smaller than the opening of the PAD connection line.

3. The method for preventing PCB board PAD deformation according to claim 1, characterized in that, The method for generating the window at the connection between the PAD and the circuit connection line includes the following steps: Design the window size of the PAD and the circuit connection line, and generate corresponding pre-window marking points on the film; The pre-windowed marking points are generated on the PCB board through dry film processing, exposure, and development steps. Finally, during the solder resist windowing process, the solder resist ink on the pre-opening window marking points is removed to generate a PAD connection line window of the corresponding size.

4. The method for preventing PCB board PAD deformation according to claim 3, characterized in that, The method for removing solder resist ink from the pre-opened window marking points includes the following steps: First, coat the PCB surface with a layer of liquid photosensitive solder resist ink; Based on the designed window size at the connection point between the PAD and the circuit connection line, the area requiring the window is precisely exposed using a high-power lighting device, causing the solder resist ink in that area to cure. Remove the unexposed solder resist ink to complete the window opening.

5. A method for preventing PCB board PAD deformation according to claim 4, characterized in that, The high-power lighting device is an ultraviolet (UV) laser.

6. The method for preventing PCB board PAD deformation according to claim 1, characterized in that, The cleaning agent is a developer.

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