A method for solving the oil leakage problem of large-aperture plugging development

Abstract

The present invention discloses a method for solving the problem of oil leakage during development of large-aperture plugging holes, comprising the following steps: preparing a production board, wherein the production board is provided with large holes with an aperture of ≥0.6 mm; performing a resin plugging operation on the non-windowed surface corresponding to the large hole in the production board to fill the large hole with resin ink, and the plugging depth does not exceed half of the depth of the large hole; pre-baking the production board to initially solidify the resin ink in the large hole; exposing both sides of the production board by using an exposure film, wherein the exposure film is provided with a light-transmitting point with an aperture larger than the large hole at the corresponding large hole to expose and solidify the ink in the large hole; performing development and baking treatments on the production board in sequence to completely solidify the resin ink in the large hole. In the method of the present invention, large-aperture plugging holes are treated separately, and the ink in the hole is solidified before development, thereby solving the problem of oil leakage on the pad during development.

Description

Technical Field

[0001] The invention relates to the technical field of printed circuit board manufacturing, and in particular to a method for solving the problem of oil leakage during development of large-aperture plug holes. Background Art

[0002] With the development of miniaturization of electronic components, the wiring design and graphic design of the PCB industry have also changed to adapt to the high-density and high-integration circuit manufacturing. In the existing circuit board production process, for circuit boards with solder mask protection and plugging of vias, for some special structures, such as single-sided window opening, single-sided oil covering and plugging design of the hole in the solder mask pad, after the solder mask is developed, there will be abnormal problems such as oil on the PAD on the window surface of the hole in the pad, which will affect the first-time pass rate and appearance of the solder mask. In severe cases, it will also cause disconnection and functional problems of customer mounting. With the rapid development of the PCB industry, quality requirements have become increasingly stringent. For boards with such special structures, how to control and reduce the occurrence of defects and customer complaints has become an important task for process engineers.

[0003] The oil oozing problem is one of the difficulties in the process of solder mask ink. The main reason is that the pre-baking after solder mask plugging cannot cure the plugging ink, and the resin content of the plugging ink is much higher than the surface oil. When exposed together with the surface oil, there is also a problem of insufficient exposure energy, resulting in poor photocuring effect of the ink in the hole. During the development process and water washing process during the development treatment, the uncured plugging ink in the hole gushes like mud from a volcanic eruption, causing the pad (the position where the tinning of the client's patch is applied) to stick to the ink, resulting in poor tinning functionality. The scrapping of PCB boards, customer complaints, compensation and fines are all costs that PCB board manufacturers cannot afford, and the impact is huge. Summary of the invention

[0004] In view of the above-mentioned existing technical defects, the present invention provides a method for solving the problem of oil leakage during development of large-aperture plug holes. The large-aperture plug holes are treated separately and the ink in the holes is solidified before development, thereby solving the problem of oil leakage onto the pad during development.

[0005] In order to solve the above technical problems, the present invention provides a method for solving the oil leakage in large-aperture plugging development, comprising the following steps:

[0006] S1. Prepare a production plate, wherein the production plate is provided with large holes with a hole diameter ≥ 0.6 mm;

[0007] S2. Perform a resin plugging operation on the non-windowed surface corresponding to the large hole in the production board to fill the large hole with resin ink, and the plugging depth does not exceed half of the depth of the large hole;

[0008] S3, pre-baking the production board to initially solidify the resin ink in the macropores;

[0009] S4, exposing both sides of the production board by using an exposure film, wherein the exposure film is provided with a light-transmitting point having a larger aperture than the large hole at a position corresponding to the large hole, so as to expose and cure the ink in the large hole;

[0010] S5. Perform development treatment and baking treatment on the production board in sequence to completely solidify the resin ink in the macropores.

[0011] Furthermore, in step S2, when plugging the hole, the window surface at the corresponding large hole in the production board is set facing downward, and a piece of white paper is placed under the production board to detect whether resin ink flows out from the bottom of the large hole when plugging the hole.

[0012] Furthermore, in step S2, the viscosity of the resin ink is ≥200 dpa.s.

[0013] Further, in step S3, the production board is pre-baked at 60-80° C. for 1-2 h.

[0014] Furthermore, in step S4, the aperture of the light-transmitting point is 200 μm larger than the aperture of the large hole.

[0015] Furthermore, in step S4, the exposure scale during exposure is controlled at ≥10 levels.

[0016] Furthermore, in step S4, the exposure energy during exposure is ≥ 2400 mj.

[0017] Furthermore, after step S5, the following steps are also included:

[0018] S6. Screen-print solder resist ink on both surfaces of the production board, and then pre-bake the production board to initially solidify the solder resist ink;

[0019] S7, making solder resist layers on both surfaces of the production board by sequentially exposing and developing;

[0020] S8. Finally, the production board is baked.

[0021] Furthermore, the production board is a multi-layer board in which an inner core board and an outer copper foil are pressed together by a semi-cured sheet, and the multi-layer board has been sequentially subjected to the processes of drilling, copper deposition, full-board electroplating and outer layer circuit production.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] In the present invention, for the plugging treatment of large holes, the plugging process and the solder mask surface oil production process are carried out separately, and the plugging treatment for large apertures is placed before the solder mask surface oil treatment. The window opening surface and the non-window opening surface of the large hole of the production board are first identified, and then the non-window opening surface is semi-plugged to avoid the problem that the resin ink overflows to the window opening surface during the plugging process, resulting in the inability to expose the window opening surface. After pre-baking, the ink in the hole is solidified by exposure. During exposure, since there is no ink on the board surface, the surface oil on the window opening surface will not be solidified due to the increase of the exposure point, so that the size of the light-transmitting point can be designed to be larger than the aperture of the large hole, avoiding the poor accuracy of the exposure instrument. The exposure is offset due to the difference in the exposure, so that the plugging ink in the large hole can be fully photopolymerized on both sides, which solves the problem of poor exposure in the prior art that the size of the light-transmitting point cannot be larger than the hole because the surface oil and the ink in the hole need to be exposed at the same time when the plugging hole and the surface oil are made together. Then, the dirty and sticky ink on the board surface is removed through development treatment. During the development treatment, the ink in the hole has been exposed and solidified, so that the ink in the hole will not ooze out. This solves the problem of oil oozing onto the pad during development, reduces the time spent by personnel to adjust development parameters, and reduces the repair and scrapping costs of defective boards by PCB board manufacturers.

[0024] Secondly, for the method of individual plugging hole treatment, the exposure energy can be set individually for the hole during exposure, so that the photopolymerization reaction and curing effect of the ink in the hole can be improved by increasing the exposure energy. When the plug hole and the surface oil are made together in the existing method, the exposure energy must be controlled within the design range of the surface oil, which is generally around 800mj. This easily leads to unsatisfactory photocuring effect of the ink in the plug hole. In the present invention, the exposure energy is designed to be 2400mj or above, which is three times or more of the existing exposure energy of 800mj. DETAILED DESCRIPTION

[0025] In order to more fully understand the technical content of the present invention, the technical solution of the present invention will be further introduced and illustrated in conjunction with specific embodiments below.

[0026] Example

[0027] The present embodiment shows a method for manufacturing a circuit board, which includes a single plugging process of a large hole, and includes the following processing steps in sequence:

[0028] (1) Cutting: Cut the core board according to the panel size of 520mm×620mm. The thickness of the core board is 0.5mm, and the thickness of the copper layer on both surfaces of the core board is 0.5oz.

[0029] (2) Inner layer circuit production (negative film process): Inner layer pattern transfer, use a vertical coating machine to coat the photosensitive film, the film thickness of the photosensitive film is controlled to 8μm, and a fully automatic exposure machine is used to complete the exposure of the inner layer circuit with a 5-6 grid exposure ruler (21 grid exposure ruler). After development, the inner layer circuit pattern is formed; inner layer etching, the exposed and developed core board is etched to etch the inner layer circuit, and the inner layer line width is measured to be 3mil; inner layer AOI, and then check the inner layer circuit for defects such as open short circuits, circuit gaps, and circuit pinholes. Defective products are scrapped, and non-defective products are sent to the next process.

[0030] (3) Lamination: The browning speed is based on the browning thickness of the bottom copper. The core board, prepreg, and outer copper foil are laminated in sequence as required. Then, appropriate lamination conditions are selected according to the Tg of the sheet material to laminate the laminated board to form a production board.

[0031] (4) Drilling: Based on the existing drilling technology, drilling is performed on the production board according to the design requirements, and the drilled holes include large holes with a diameter ≥ 0.6 mm.

[0032] (5) Copper plating: A thin layer of copper is deposited on the board surface and hole wall by chemical copper plating. The backlight test is level 10, and the thickness of the copper plating in the hole is 0.5μm.

[0033] (6) Full-board electroplating: Full-board electroplating is performed for 120 minutes at a current density of 18 ASF to thicken the copper layer on the hole and the board surface.

[0034] (7) Production of outer circuit (positive film process): Transfer of outer pattern, using fully automatic exposure machine and positive circuit film, with 5-7 grid exposure ruler (21 grid exposure ruler) to complete the exposure of outer circuit, after development, the outer circuit pattern is formed on the production board; electroplating of outer pattern, and then copper plating and tin plating on the production board respectively, setting the electroplating parameters according to the required copper thickness, copper plating is 1.8ASD current density electroplating for 60 minutes on the whole board, tin plating is 1.2ASD current density electroplating for 10 minutes, tin thickness 3-5μm; then stripping, etching and tin stripping in turn, etching the outer circuit on the production board, the copper thickness of the outer circuit is greater than or equal to 70μm; outer layer AOI, using automatic optical inspection system, by comparing with CAM data, to detect whether the outer circuit has defects such as open circuit, gap, incomplete etching, short circuit, etc.

[0035] (8) Single plugging hole treatment: specifically including the following steps:

[0036] a. First, identify the window surface and non-window surface corresponding to the large hole in the production board. The window surface refers to the side where there is no solder mask ink around the hole mouth of the large hole. The later surface treatment is used for welding with external electronic components. The non-window surface is the side covered with a solder mask protective layer around the hole mouth during soldering. Through the method of controlling the depth of the hole, the resin plugging operation is performed on the non-window surface corresponding to the large hole in the production board to fill the large hole with resin ink, and the plugging depth does not exceed half of the large hole depth. Preferably, the plugging depth is half of the opening depth to form a semi-plugging design.

[0037] In the above, when plugging the hole, the window surface corresponding to the large hole in the production board is set downward, and a piece of white paper is placed under the production board to detect whether resin ink flows out from the bottom of the large hole when plugging the hole, thereby facilitating quality inspection during plugging. Whether the plugging is qualified can be judged directly by visual inspection without additional testing; of course, an air guide hole with a smaller aperture than the large hole will be provided at the position corresponding to the large hole on the white paper.

[0038] In the above, the viscosity of the resin ink is ≥200dpa.s. High-viscosity resin ink is used for plugging holes to prevent the resin ink from flowing down to the window surface due to its high fluidity during plugging, thereby contaminating the window surface.

[0039] b. Pre-bake the production board at 60-80℃ for 1-2h to initially solidify the resin ink in the macropores to form a semi-cured state.

[0040] c. Expose both sides of the production board through exposure film, wherein the exposure film is provided with light-transmitting points with a larger aperture than the large hole at the corresponding large hole, so as to expose and cure the resin ink in the large hole on both sides.

[0041] In the above, the aperture of the light-transmitting point is 200μm larger than the aperture of the large hole. The appropriate increase in the light-transmitting reaction area can avoid the influence of the exposure accuracy error, so that the plugging ink in the large hole can be fully photopolymerized on both sides, thereby solving the problem in the prior art that the size of the light-transmitting point cannot be larger than the hole due to the need to expose the surface oil and the ink in the hole at the same time when the plug hole and the surface oil are made together, resulting in poor exposure.

[0042] In the above, the exposure scale during exposure is controlled at ≥10 levels, and the exposure energy during exposure is ≥2400mj; for the method of individual plugging treatment, the exposure energy can be set individually for the hole during exposure, so that the photopolymerization reaction and curing effect of the ink in the hole can be improved by increasing the exposure energy. When the plug hole and the surface oil are made together in the existing method, the exposure energy needs to be controlled within the design range of the surface oil, which is generally around 800mj, and the photocuring effect of the ink in the plug hole is prone to unsatisfactory. In the present invention, the exposure energy is designed to be 2400mj or above, which is three times or more of the existing exposure energy of 800mj.

[0043] d. Develop the production board to remove ink and other dirt on the board surface.

[0044] e. Finally, the production board is subjected to high-temperature baking treatment to completely solidify the resin ink in the macropores; the baking temperature is 150°C and the time is 60 minutes.

[0045] (9) Solder mask and silk screen characters: After the solder mask ink is silk screen printed on the surface of the production board, it is subjected to pre-baking, initial curing, exposure, development and heat curing treatments in sequence to solidify the solder mask ink into a solder mask layer; specifically, a "UL mark" is added to the solder mask ink on the TOP surface and the characters on the TOP surface, thereby coating a layer on the circuits and substrates that do not require soldering to prevent bridging between circuits during soldering, provide a permanent electrical environment and resist chemical corrosion, and at the same time beautify the appearance.

[0046] (10) Surface treatment (nickel-gold deposition): The copper surface of the pad at the solder mask opening is chemically treated to uniformly deposit nickel and gold layers of a certain required thickness. The nickel layer thickness is 3-5 μm; the gold layer thickness is 0.05-0.1 μm.

[0047] (11) Electrical test: Test the electrical conductivity of the finished board. The test method used for this board is: flying probe test.

[0048] (12) Molding: According to the existing technology and the design requirements, the circuit board is manufactured with a shape tolerance of + / -0.05mm.

[0049] (13) FQC: Inspect the appearance of the circuit board according to the customer's acceptance standards and our inspection standards. If there are any defects, repair them in time to ensure that we provide customers with excellent quality control.

[0050] (14) FQA: Re-test the circuit board’s appearance, hole copper thickness, dielectric layer thickness, green oil thickness, inner layer copper thickness, etc. to see if they meet customer requirements.

[0051] (15) Packaging: According to the packaging method and packaging quantity required by the customer, the circuit boards are sealed and packed with desiccant and humidity card before shipment.

[0052] The technical solutions provided by the embodiments of the present invention are introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only applicable to help understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, according to the embodiments of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for solving the oil leakage in large-aperture plugging development, characterized in that: The following steps are involved: S1. Prepare a production plate, wherein the production plate is provided with large holes with a hole diameter ≥ 0.6 mm; S2. Perform a resin plugging operation on the non-windowed surface corresponding to the large hole in the production board to fill the large hole with resin ink, and the plugging depth does not exceed half of the depth of the large hole; S3, pre-baking the production board to initially solidify the resin ink in the macropores; S4, exposing both sides of the production board by using an exposure film, wherein the exposure film is provided with a light-transmitting point having a larger aperture than the large hole at the position corresponding to the large hole, so as to expose and cure the ink in the large hole; the aperture of the light-transmitting point is 200 μm larger than the aperture of the large hole; S5, sequentially performing development treatment and baking treatment on the production board to completely solidify the resin ink in the macropores; S6. Screen-print solder resist ink on both surfaces of the production board, and then pre-bake the production board to initially solidify the solder resist ink; S7, making solder resist layers on both surfaces of the production board by sequentially exposing and developing; S8. Finally, the production board is baked.

2. The method for solving the oil leakage in large-aperture plugging development according to claim 1 is characterized in that: In step S2, when plugging the hole, the window surface at the corresponding large hole in the production board is set downward, and a piece of white paper is placed under the production board to detect whether resin ink flows out from the bottom of the large hole when plugging the hole.

3. The method for solving the oil leakage in large-aperture plugging development according to claim 1, characterized in that: In step S2, the viscosity of the resin ink is ≥200 dpa.s.

4. The method for solving the oil leakage in large-aperture plugging development according to claim 1, characterized in that: In step S3, the production board is pre-baked at 60-80°C for 1-2h.

5. The method for solving the oil leakage in large-aperture plugging development according to claim 1, characterized in that: In step S4, the exposure scale during exposure is controlled at ≥10 levels.

6. The method for solving the oil leakage in large-aperture plugging development according to claim 1, characterized in that: In step S4, the exposure energy during exposure is ≥ 2400 mj.

7. The method for solving the oil leakage in large-aperture plugging development according to claim 1, characterized in that: The production board is a multi-layer board in which an inner core board and an outer copper foil are pressed together by a semi-cured sheet, and the multi-layer board has been through the processes of drilling, copper deposition, full-board electroplating and outer layer circuit making in sequence.