Preparation method of PCB (Printed Circuit Board)

Abstract

The invention discloses a preparation method of a PCB (Printed Circuit Board), which belongs to the technical field of PCBs and comprises the following steps of: (1) silk-screening ink on a PCB substrate, and sequentially pre-baking, exposing, developing, baking, UV (Ultraviolet) photocuring and pickling; (2) carrying out silk-screen printing of photosensitive ink on the pickled PCB substrate, and successively carrying out baking, exposure and development; (3) carrying out nickel-gold immersion treatment on the PCB substrate so as to deposit a nickel-gold layer on the surface of the PCB substrate; and (4) carrying out board milling on the PCB substrate to obtain the PCB printed circuit board. The straightening treatment is added after the PCB substrate is subjected to routing, the straightening parameters are controlled, and the ink curing degree is improved and the surface is recombined at high temperature / certain pressure, so that the contact angle of the ink surface is changed, the contact angle of the ink surface is effectively improved, and the requirements of customers are met; and finally, the scrapping caused by substandard ink contact angle is reduced, and the economic benefit is improved.

Description

Technical Field

[0001] The invention relates to the technical field of PCB printed circuit boards, and in particular to a method for preparing a PCB printed circuit board. Background Art

[0002] In PCB printed circuit boards, in order to cope with the newly added ink surface contact angle detection project, when the ink contact angle is abnormal, the following will appear Figure 1 The solder beads have poor wetting and are difficult to spread when mounting the parts shown. After internal testing, research and analysis, it was found that the differences in different production processes lead to certain differences in the contact angle of the ink surface. At present, there is a blank area in the industry's research on contact angle in the solder mask printing process. The factors affecting the contact angle of the solder mask process and the process level are still unclear. In addition, the client is faced with returns and complaints due to poor tin wetting. In addition, the current process has an ink contact angle that exceeds the standard (75+ / -15 degrees, DI underwater), and Cpk cannot meet the requirements.

[0003] Wetting: When a drop of water is dropped onto a solid surface, during the contact between the liquid and the solid, the solid-liquid interface gradually replaces the gas-liquid interface and the gas-solid interface. This process is called wetting. Surface energy is the non-volume work done on a substance in order to reversibly increase the surface area of ​​a system under the conditions of constant temperature, constant pressure, and constant humidity. It can measure the surface tension of a substance. Liquid drops onto a solid surface, and as the liquid spreads, it covers the solid surface, forming a drop that rests on its surface. We use the contact angle to describe the shape of the drop formed by the liquid and the solid plane. The accurate contact angle is the angle θ from the solid-liquid interface through the liquid interior to the gas interface at the junction of the solid, liquid, and gas phases. Among them, Figure 2 The formula shown is the basic formula for wetting, also known as the wetting equation, which can be regarded as the result of the balance of three interfacial tensions at the junction of three phases. In specific applications, we use the size of the contact angle as an important indicator for judging wettability.

[0004] like Figure 3 As shown in the figure, the following process points are selected to measure the contact angle during the preparation of PCB printed circuit boards: (1) Measurement after UV curing: After UV curing, the thermal curing and light curing of the ink have been completed, and the basic properties of the ink have been stabilized; (2) After immersion gold film stripping: immersion gold needs to be attacked by a variety of chemicals, and the film stripping chemicals are also very aggressive to the ink, and the contact angle of the ink surface decreases to a certain extent; (3) After OSP+ cleaning: When the finished product is packaged, the contact angle of the ink surface is similar to that after immersion gold film stripping, but there is a risk of exceeding the lower limit at a single point (75 degrees + / - 15 degrees); Among them, the contact angle of the ink surface decreases accordingly from UV curing to immersion gold and after OSP.

[0005] In view of this, this application is filed. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing a PCB printed circuit board, which effectively improves the contact angle of the ink surface to meet customer requirements (75+ / -15 degrees, cpk>1.33), ultimately reducing the scrapping caused by the ink contact angle not meeting the standard and improving economic benefits.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A method for preparing a PCB printed circuit board comprises the following steps:

[0009] (1) Screen printing ink on PCB substrate, followed by pre-baking, exposure, development, baking, UV light curing, and pickling;

[0010] (2) Screen printing photosensitive ink on the pickled PCB substrate, followed by baking, exposure, and development;

[0011] (3) performing a nickel-gold treatment on the PCB substrate to deposit a nickel-gold layer on the surface of the PCB substrate;

[0012] (4) The PCB substrate is plated to obtain a PCB printed circuit board.

[0013] As a preferred embodiment of the present invention, after the PCB substrate is gonged, a straightening step is further included, and the straightening step is specifically: treating the PCB substrate at 150-165° C. and 5-7 kg pressure for 1-3 hours.

[0014] The present invention creatively adds a straightening treatment to the PCB substrate after gonging, and controls the straightening parameters, thereby improving the curing degree of the ink and reorganizing the surface under high temperature / certain pressure, thereby changing the contact angle of the ink surface, effectively improving the contact angle of the ink surface to meet customer requirements (75+ / -15 degrees, cpk>1.33), and ultimately reducing the scrap caused by the ink contact angle not meeting the standard, thereby improving economic benefits.

[0015] As a preferred embodiment of the present invention, the energy of the UV light curing is A, 800mj / cm 2 ≤A≤1200mj / cm 2 Among them, UV light curing can effectively improve the light curing rate of ink, and the curing rate reaches more than 90%.

[0016] As a preferred embodiment of the present invention, after the nickel-gold layer is deposited on the surface of the PCB substrate, UV light curing is also included, and the energy of the UV light curing is B, satisfying: 0.4A≤B≤2A.

[0017] The present invention creatively performs UV light curing again after the nickel-gold layer is deposited on the surface of the PCB substrate, which effectively improves the ink surface curing rate, reduces the ink surface roughness, and increases the ink surface contact angle, thereby meeting customer requirements (75+ / -15 degrees, cpk>1.33) and ultimately reduces the scrapping caused by the ink contact angle not meeting the standard, thereby improving economic benefits.

[0018] Without optimized design, the scrap rate of ink surface contact angle exceeding the standard is 4-5%. With the solution of the present invention, the scrap rate is 0.2-0.3%.

[0019] As a preferred embodiment of the present invention, the coating thickness of the ink in step (1) is 18 to 21 μm;

[0020] The coating thickness of the photosensitive ink in the step (2) is 18 to 21 μm.

[0021] As a preferred embodiment of the present invention, the pre-baking temperature in step (1) is 75-80° C., and the pre-baking time is 20-40 minutes; through the specific low-temperature pre-baking, the organic solvent in the ink on the board surface can be volatilized.

[0022] The baking temperature in step (1) is 145-155° C. and the baking time is 40-80 min.

[0023] The baking temperature in step (2) is 75-80° C., and the pre-baking time is 20-40 minutes.

[0024] As a preferred embodiment of the present invention, the exposure energy in step (1) is 70 to 80 mj / cm 2 ;

[0025] The exposure energy in step (2) is 280-300 mj / cm 2 .

[0026] As a preferred embodiment of the present invention, the step (1) of developing is specifically as follows: immersing the PCB substrate in a developer at 45-50° C. for 40-60 seconds, and then drying at 75-85° C.;

[0027] The development in step (2) is specifically as follows: immersing the PCB substrate in a developer at 45-50° C. for 40-60 seconds, and then drying at 75-85° C.

[0028] As a preferred embodiment of the present invention, the immersion of the PCB substrate in a nickel-gold immersion solution for nickel-gold immersion treatment is specifically as follows: a nickel-gold immersion area and a non-nickel-gold immersion treatment area are provided on the PCB substrate, nickel-gold is immersed on the surface of the PCB substrate by chemical replacement, and the photosensitive ink of the non-nickel-gold immersion treatment area is removed by an organic film-removing solution.

[0029] As a preferred embodiment of the present invention, the gong plate specifically divides the PCB substrate into PCB unit boards.

[0030] As a preferred embodiment of the present invention, before screen printing the ink on the PCB substrate, the copper surface of the PCB substrate is micro-etched with an organic acid, and the micro-etching thickness is 1.1 to 1.2 μm.

[0031] As a preferred embodiment of the present invention, the organic acid includes at least one of sulfuric acid, formic acid, nitric acid and hydrofluoric acid.

[0032] As a preferred embodiment of the present invention, the pickling is specifically carried out by using sulfuric acid with a mass fraction of 4 to 10%.

[0033] The beneficial effects of the present invention are as follows: (1) The present invention adds a straightening treatment after the PCB substrate is grouted, and controls the parameters of the straightening treatment. Under high temperature / certain pressure, the curing degree of the ink is improved and the surface is reorganized, thereby changing the contact angle of the ink surface, effectively improving the contact angle of the ink surface, and meeting the customer's requirements (75+ / -15 degrees, cpk>1.33). Ultimately, the scrapping caused by the ink contact angle not meeting the standard is reduced, and the economic benefits are improved. (2) The present invention performs UV light curing again after the nickel-gold layer is deposited on the surface of the PCB substrate, effectively improving the ink surface curing rate, reducing the ink surface roughness, and improving the ink surface contact angle, thereby meeting the customer's requirements (75+ / -15 degrees, cpk>1.33). Ultimately, the scrapping caused by the ink contact angle not meeting the standard is reduced, and the economic benefits are improved. (3) Without optimized design, the scrapping rate of the ink surface contact angle exceeding the standard is 4-5%; using the scheme of the present invention, the scrapping rate is 0.2-0.3%. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a diagram showing that when the ink contact angle is abnormal in the background technology, there is poor tin bead wetting during mounting.

[0035] Figure 2 Figure 1 is a basic formula for wetting.

[0036] Figure 3 In order to select process points to measure the contact angle diagram during the preparation of PCB printed circuit boards.

[0037] Figure 4 The contact angle diagrams of Examples 1 to 3 and Comparative Example 1 are shown. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application are described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0039] In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0040] In this application, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are deemed to be continuous and include the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0041] In the present application, there is no particular limitation on the specific dispersion and stirring treatment methods.

[0042] Unless otherwise specified, the components, raw materials or instruments used in the embodiments and comparative examples of the present invention are all commercially available raw materials or instruments, and the components and raw materials used in each parallel experiment are all of the same kind.

[0043] The following examples are provided to facilitate understanding of the present invention. These examples are not provided to limit the scope of the claims.

[0044] Example 1

[0045] A method for preparing a PCB printed circuit board comprises the following steps

[0046] (1) The copper surface of the PCB substrate is micro-etched with a mixed acid of sulfuric acid solution and formic acid to a micro-etching thickness of 1.2 μm;

[0047] (2) Taiyo PSR-4000D10ME ink (viscosity 80-120 dpas) was applied by screen printing (68T mesh) with a coating thickness of 20 μm;

[0048] Pre-bake the PCB substrate, where the top side is 75 degrees * 25 minutes, and the bot side is 78 degrees * 38 minutes.

[0049] The PCB substrate was exposed using an LDI exposure machine with an exposure energy of 75mj / cm 2, 6 levels (21-level exposure scale).

[0050] The PCB substrate is immersed in 8% g / L sodium carbonate solution for 50s for development, the development temperature is 48 degrees, the upper pressure of the development section / washing section is 1.7 bar, the lower pressure of the development section / washing section is 1.3 bar, the drying temperature is 80+ / -5 degrees, and the drying time is 25s. From the washing section to the drying section, at least 2 pairs of absorbent sponges (2 each on the upper and lower sides, a total of 4) are required to absorb water stains on the ink surface before drying, otherwise the ink surface will be affected and contaminated;

[0051] Bake the PCB substrate at 150°C for 60 minutes;

[0052] The PCB substrate is heated to 1000 mj / cm 2 Curing for 45 seconds;

[0053] The PCB substrate is pickled with a 5% sulfuric acid solution;

[0054] (3) The OSP area (non-nickel-gold immersion area) is selectively printed with photosensitive oil in the OSP area by screen printing (43T screen, photosensitive ink is TaiyoPPR-EB02) and single baking and single printing, with a thickness of 20μm. The baking parameters are: low temperature baking, top surface 75 degrees * 25 minutes, bot surface 78 degrees * 38 minutes;

[0055] After baking, exposure and development in sequence;

[0056] Among them, exposure parameters: ORC parallel light film exposure machine, exposure energy 300mj / cm 2 , exposure level 6 (21-level exposure scale);

[0057] Development parameters: soak in 8% g / L sodium carbonate solution for 50s, development temperature is 48 degrees, upper pressure of development section / washing section is 1.7 bar, lower pressure of development section / washing section is 1.3 bar, drying temperature is 80+ / -5 degrees, drying time is 25s, and at least 2 pairs of absorbent sponges (2 each on the upper and lower sides, a total of 4) are required from the washing section to the drying section;

[0058] (3) performing a nickel-gold treatment on the PCB substrate to deposit a nickel-gold layer on the surface of the PCB substrate;

[0059] Specifically, in the gold-immersion area (non-photosensitive oil OSP), a nickel-gold layer is formed on the copper surface by chemical replacement (referred to as chemical nickel-gold) to form a gold surface pad. After gold-immersion, an organic film-removing solution (organic alkali system) is used to remove the photosensitive oil in the OSP area to expose the OSP copper surface area. This process is aggressive to the ink surface. The film-removing time is controlled to be 90s, the film-removing point is 40%, and the film-removing temperature is 50°C. Otherwise, the ink is prone to whitening / peeling, and the ink contact angle is abnormal.

[0060] (4) dividing the PCB substrate into PCB unit boards;

[0061] (5) Straightening: The PCB substrate is treated at 150° C. and 5 kg pressure for 2 h to obtain a PCB printed circuit board.

[0062] Example 2

[0063] The difference between Example 2 and Example 1 is that the return straightening parameters are different, and the others are the same.

[0064] In this embodiment, the PCB substrate is treated at 150° C. and 7 kg pressure for 2 hours.

[0065] Example 3

[0066] The difference between Example 3 and Example 1 is that the return straightening parameters are different, and the others are the same.

[0067] In this embodiment, the PCB substrate is treated at 160° C. and 5 kg pressure for 2 hours.

[0068] Example 4

[0069] The difference between Example 4 and Example 1 is that the return straightening parameters are different, and the others are the same.

[0070] In this embodiment, the PCB substrate is treated at 140° C. and 5 kg pressure for 2 hours.

[0071] Example 5

[0072] The difference between Example 5 and Example 1 is that the return straightening parameters are different, and the others are the same.

[0073] In this embodiment, the PCB substrate is treated at 170° C. and 5 kg pressure for 2 hours.

[0074] Example 6

[0075] The difference between Example 6 and Example 1 is that the return straightening parameters are different, and the others are the same.

[0076] In this embodiment, the PCB substrate is treated at 150° C. and 3 kg pressure for 2 hours.

[0077] Example 7

[0078] The difference between Example 7 and Example 1 is that the return straightening parameters are different, and the others are the same.

[0079] In this embodiment, the PCB substrate is treated at 150° C. and 8 kg pressure for 2 hours.

[0080] Example 8

[0081] A method for preparing a PCB printed circuit board comprises the following steps

[0082] (1) The copper surface of the PCB substrate is micro-etched with a mixed acid of sulfuric acid solution and formic acid to a micro-etching thickness of 1.2 μm;

[0083] (2) Taiyo PSR-4000D10ME ink (viscosity 80-120 dpas) was applied by screen printing (68T mesh) with a coating thickness of 20 μm;

[0084] Pre-bake the PCB substrate, where the top side is 75 degrees * 25 minutes, and the bot side is 78 degrees * 38 minutes.

[0085] The PCB substrate was exposed using an LDI exposure machine with an exposure energy of 75mj / cm 2 , 6 levels (21-level exposure scale).

[0086] The PCB substrate is immersed in 8% g / L sodium carbonate solution for 50s for development, the development temperature is 48 degrees, the upper pressure of the development section / washing section is 1.7 bar, the lower pressure of the development section / washing section is 1.3 bar, the drying temperature is 80+ / -5 degrees, and the drying time is 25s. From the washing section to the drying section, at least 2 pairs of absorbent sponges (2 each on the upper and lower sides, a total of 4) are required to absorb water stains on the ink surface before drying, otherwise the ink surface will be affected and contaminated;

[0087] Bake the PCB substrate at 150°C for 60 minutes;

[0088] The PCB substrate is heated to 1000 mj / cm 2 Curing for 45 seconds;

[0089] The PCB substrate is pickled with a 5% sulfuric acid solution;

[0090] (3) The photosensitive oil is selectively printed on the OSP area by screen printing (43T screen, photosensitive ink is Taiyo PPR-EB02) and single baking and single printing, with a thickness of 20μm. The baking parameters are: low temperature baking, top surface 75 degrees * 25 minutes, bot surface 78 degrees * 38 minutes;

[0091] After baking, exposure and development in sequence;

[0092] Among them, exposure parameters: ORC parallel light film exposure machine, exposure energy 300mj / cm 2 , exposure level 6 (21-level exposure scale);

[0093] Development parameters: soak in 8% g / L sodium carbonate solution for 50s, development temperature is 48 degrees, upper pressure of development section / washing section is 1.7 bar, lower pressure of development section / washing section is 1.3 bar, drying temperature is 80+ / -5 degrees, drying time is 25s, and at least 2 pairs of absorbent sponges (2 each on the upper and lower sides, a total of 4) are required from the washing section to the drying section;

[0094] (3) performing a nickel-gold treatment on the PCB substrate to deposit a nickel-gold layer on the surface of the PCB substrate;

[0095] Specifically, in the gold-immersion area (non-photosensitive oil OSP), a nickel-gold layer is formed on the copper surface by chemical replacement to form a gold surface pad. After gold-immersion, an organic film-removing solution (organic alkali system) is used to remove the photosensitive oil in the OSP area to expose the OSP copper surface area. This process is aggressive to the ink surface. The film-removing time is controlled to be 90s, the film-removing point is 40%, and the film-removing temperature is 50°C. Otherwise, the ink is prone to whitening / peeling, and the ink contact angle is abnormal.

[0096] (4) The PCB substrate is light-cured again with a light-curing energy of 400 mj / cm 2 , time is;

[0097] (5) Divide the PCB substrate into PCB unit boards to obtain PCB printed circuit boards.

[0098] Example 9

[0099] The difference between Example 9 and Example 8 is that the light curing energy in step (4) is different, and the others are the same.

[0100] The photocuring energy in this embodiment is 500 mj / cm 2 .

[0101] Example 10

[0102] The difference between Example 10 and Example 8 is that the light curing energy in step (4) is different, and the others are the same.

[0103] The photocuring energy in this embodiment is 1000 mj / cm 2 .

[0104] Embodiment 11

[0105] The difference between Example 11 and Example 8 is that the light curing energy in step (4) is different, and the rest is the same.

[0106] The photocuring energy in this embodiment is 2000 mj / cm 2 .

[0107] Example 12

[0108] The difference between Example 12 and Example 8 is that the light curing energy in step (4) is different, and the rest is the same.

[0109] The photocuring energy in this embodiment is 200 mj / cm 2 .

[0110] Comparative Example 1

[0111] A method for preparing a PCB printed circuit board comprises the following steps

[0112] (1) The copper surface of the PCB substrate is micro-etched with a mixed acid of sulfuric acid solution and formic acid to a micro-etching thickness of 1.2 μm;

[0113] (2) Taiyo PSR-4000D10ME ink (viscosity 80-120 dpas) was applied by screen printing (68T mesh) with a coating thickness of 20 μm;

[0114] Pre-bake the PCB substrate, where the top side is 75 degrees * 25 minutes, and the bot side is 78 degrees * 38 minutes.

[0115] The PCB substrate was exposed using an LDI exposure machine with an exposure energy of 75mj / cm 2 , 6 levels (21-level exposure scale).

[0116] The PCB substrate is immersed in 8% g / L sodium carbonate solution for 50s for development, the development temperature is 48 degrees, the upper pressure of the development section / washing section is 1.7 bar, the lower pressure of the development section / washing section is 1.3 bar, the drying temperature is 80+ / -5 degrees, and the drying time is 25s. From the washing section to the drying section, at least 2 pairs of absorbent sponges (2 each on the upper and lower sides, a total of 4) are required to absorb water stains on the ink surface before drying, otherwise the ink surface will be affected and contaminated;

[0117] Bake the PCB substrate at 150°C for 60 minutes;

[0118] The PCB substrate is heated to 1000 mj / cm 2 Curing for 45 seconds;

[0119] The PCB substrate is pickled with a 5% sulfuric acid solution;

[0120] (3) The photosensitive oil is selectively printed on the OSP area by screen printing (43T screen, photosensitive ink is Taiyo PPR-EB02) and single baking and single printing, with a thickness of 20μm. The baking parameters are: low temperature baking, top surface 75 degrees * 25 minutes, bot surface 78 degrees * 38 minutes;

[0121] After baking, exposure and development in sequence;

[0122] Among them, exposure parameters: ORC parallel light film exposure machine, exposure energy 300mj / cm 2 , exposure level 6 (21-level exposure scale);

[0123] Development parameters: soak in 8% g / L sodium carbonate solution for 50s, development temperature is 48 degrees, upper pressure of development section / washing section is 1.7 bar, lower pressure of development section / washing section is 1.3 bar, drying temperature is 80+ / -5 degrees, drying time is 25s, and at least 2 pairs of absorbent sponges (2 each on the upper and lower sides, a total of 4) are required from the washing section to the drying section;

[0124] (3) performing a nickel-gold treatment on the PCB substrate to deposit a nickel-gold layer on the surface of the PCB substrate;

[0125] Specifically, in the gold-immersion area (non-photosensitive oil OSP), a nickel-gold layer is formed on the copper surface by chemical replacement to form a gold surface pad. After gold-immersion, an organic film-removing solution (organic alkali system) is used to remove the photosensitive oil in the OSP area to expose the OSP copper surface area. This process is aggressive to the ink surface. The film-removing time is controlled to be 90s, the film-removing point is 40%, and the film-removing temperature is 50°C. Otherwise, the ink is prone to whitening / peeling, and the ink contact angle is abnormal.

[0126] (4) Divide the PCB substrate into PCB unit boards to obtain PCB printed circuit boards.

[0127] Comparative Example 2

[0128] The difference between Comparative Example 2 and Comparative Example 1 is that the number of UV curing times in step (2) is increased in Comparative Example 2. In this comparative example, the PCB substrate is cured three times at 1000 mj / cm2, each time

[0129] Comparative Example 3

[0130] A method for preparing a PCB printed circuit board comprises the following steps

[0131] (1) The copper surface of the PCB substrate is micro-etched with a mixed acid of sulfuric acid solution and formic acid to a micro-etching thickness of 1.2 μm;

[0132] (2) Taiyo PSR-4000D10ME ink (viscosity 80-120 dpas) was applied by screen printing (68T mesh) with a coating thickness of 20 μm;

[0133] Pre-bake the PCB substrate, where the top side is 75 degrees * 25 minutes, and the bot side is 78 degrees * 38 minutes.

[0134] The PCB substrate was exposed using an LDI exposure machine with an exposure energy of 75mj / cm 2 , 6 levels (21-level exposure scale).

[0135] The PCB substrate is immersed in 8% g / L sodium carbonate solution for 50s for development, the development temperature is 48 degrees, the upper pressure of the development section / washing section is 1.7 bar, the lower pressure of the development section / washing section is 1.3 bar, the drying temperature is 80+ / -5 degrees, and the drying time is 25s. From the washing section to the drying section, at least 2 pairs of absorbent sponges (2 each on the upper and lower sides, a total of 4) are required to absorb water stains on the ink surface before drying, otherwise the ink surface will be affected and contaminated;

[0136] The PCB substrate is heated to 1000 mj / cm 2 Lower curing

[0137] Bake the PCB substrate at 150°C for 60 minutes;

[0138] The PCB substrate is heated to 1000 mj / cm 2 Curing for 45 seconds;

[0139] The PCB substrate is pickled with a 5% sulfuric acid solution;

[0140] (3) The photosensitive oil is selectively printed on the OSP area by screen printing (43T screen, photosensitive ink is Taiyo PPR-EB02) and single baking and single printing, with a thickness of 20μm. The baking parameters are: low temperature baking, top surface 75 degrees * 25 minutes, bot surface 78 degrees * 38 minutes;

[0141] After baking, exposure and development in sequence;

[0142] Among them, exposure parameters: ORC parallel light film exposure machine, exposure energy 300mj / cm 2 , exposure level 6 (21-level exposure scale);

[0143] Development parameters: soak in 8% g / L sodium carbonate solution for 50s, development temperature is 48 degrees, upper pressure of development section / washing section is 1.7 bar, lower pressure of development section / washing section is 1.3 bar, drying temperature is 80+ / -5 degrees, drying time is 25s, and at least 2 pairs of absorbent sponges (2 each on the upper and lower sides, a total of 4) are required from the washing section to the drying section;

[0144] (3) performing a nickel-gold treatment on the PCB substrate to deposit a nickel-gold layer on the surface of the PCB substrate;

[0145] Specifically, in the gold-immersion area (non-photosensitive oil OSP), a nickel-gold layer is formed on the copper surface by chemical replacement to form a gold surface pad. After gold-immersion, an organic film-removing solution (organic alkali system) is used to remove the photosensitive oil in the OSP area to expose the OSP copper surface area. This process is aggressive to the ink surface. The film-removing time is controlled to be 90s, the film-removing point is 40%, and the film-removing temperature is 50°C. Otherwise, the ink is prone to whitening / peeling, and the ink contact angle is abnormal.

[0146] (4) Divide the PCB substrate into PCB unit boards to obtain PCB printed circuit boards.

[0147] Test Example 1

[0148] Contact angle test: The measuring instrument uses SDP-300 contact angle meter, which uses CCD to obtain the front image of the water droplet contacting the surface of the object, and then uses software to fit the shape of the water droplet to calculate the contact angle between the water droplet and the surface of the object.

[0149] Measuring liquid: DI water and CH2I2 are used to measure liquid. The two liquids have different surface tension, polarity component and dispersion component, which can be used to calculate the surface energy of the object surface.

[0150] Straight board expansion and contraction size: produce 60pnl as 1 lot, extract 5pnl / lot, and measure the difference between the expansion and contraction diagonal target distance and the design standard value.

[0151] Among them, the contact angle diagrams of Examples 1 to 3 and Comparative Example 1 are as follows: Figure 4 shown.

[0152] Table 1

[0153]

[0154] As can be seen from Table 1, the present invention adds a straightening treatment after the PCB substrate is grouted, and controls the straightening parameters. Under high temperature / certain pressure, the curing degree of the ink is improved and the surface is reorganized, thereby changing the contact angle of the ink surface, effectively improving the contact angle of the ink surface to meet customer requirements (75+ / -15 degrees, cpk>1.33), ultimately reducing the scrapping caused by the ink contact angle not meeting the standard, and improving economic benefits.

[0155] Test Example 2

[0156] The water contact angles of Examples 8 to 12 and Comparative Examples 1 to 3 were tested according to the method of Test Example 1 (no expansion or contraction of the dimensions, no expansion or contraction test was performed).

[0157] Table 2

[0158] DI water contact angle Surface condition Example 8 76.3669(passed) No abnormality Example 9 79.0595(passed) No abnormality Example 10 82.8014(Qualified) No abnormality Embodiment 11 88.5798(Qualified) No abnormality Example 12 92.1211 (Unqualified) Yellow surface Comparative Example 1 65.5739 (failed) No abnormality Comparative Example 2 93.1240 (Unqualified) Yellow surface Comparative Example 3 95.6421 (failed) Yellowing surface

[0159] It can be seen from Table 2 that the present invention performs UV light curing again after the nickel-gold layer is deposited on the surface of the PCB substrate, which effectively improves the ink surface curing rate, reduces the ink surface roughness, and increases the ink surface contact angle, thereby meeting customer requirements (75+ / -15 degrees, cpk>1.33) and ultimately reduces the scrapping caused by the ink contact angle not meeting the standard, thereby improving economic benefits.

[0160] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing a PCB printed circuit board, characterized in that: The following steps are involved: (1) Screen printing ink on PCB substrate, followed by pre-baking, exposure, development, baking, UV light curing, and pickling; (2) Screen printing photosensitive ink on the pickled PCB substrate, followed by baking, exposure, and development; (3) performing a nickel-gold treatment on the PCB substrate to deposit a nickel-gold layer on the surface of the PCB substrate; (4) The PCB substrate is plated to obtain a PCB printed circuit board.

2. The method for preparing a PCB printed circuit board according to claim 1, characterized in that: After the PCB substrate is grouted, a straightening step is also included. The straightening step is specifically: treating the PCB substrate at 150-165° C. and 5-7 kg pressure for 1-3 hours.

3. The method for preparing a PCB printed circuit board according to claim 1, characterized in that: The energy of the UV light curing is A, 800mj / cm 2 ≤A≤1200mj / cm 2 .

4. The method for preparing a PCB printed circuit board according to claim 2, characterized in that: After the nickel-gold layer is deposited on the surface of the PCB substrate, UV light curing is also included, and the energy of the UV light curing is B, which satisfies: 0.4A≤B≤2A.

5. The method for preparing a PCB printed circuit board according to claim 1, characterized in that: The coating thickness of the ink in step (1) is 18 to 21 μm; The coating thickness of the photosensitive ink in the step (2) is 18 to 21 μm.

6. The method for preparing a PCB printed circuit board according to claim 1, characterized in that: The pre-baking temperature in step (1) is 75-80° C., and the pre-baking time is 20-40 min; The baking temperature in step (1) is 145-155° C. and the baking time is 40-80 min. The baking temperature in step (2) is 75-80° C., and the pre-baking time is 20-40 minutes.

7. The method for preparing a PCB printed circuit board according to claim 1, characterized in that: The exposure energy in step (1) is 70-80 mj / cm 2 ; The exposure energy in step (2) is 280-300 mj / cm 2 .

8. The method for preparing a PCB printed circuit board according to claim 1, characterized in that: The step (1) of developing specifically comprises: immersing the PCB substrate in a developer at 45-50° C. for 40-60 seconds, and then drying at 75-85° C.; The development in step (2) is specifically as follows: immersing the PCB substrate in a developer at 45-50° C. for 40-60 seconds, and then drying at 75-85° C.

9. The method for preparing a PCB printed circuit board according to claim 1, characterized in that: The method of immersing the PCB substrate in a nickel-gold immersion solution for nickel-gold immersion treatment is specifically as follows: a nickel-gold immersion area and a non-nickel-gold immersion treatment area are provided on the PCB substrate, nickel-gold is immersed on the surface of the PCB substrate by chemical replacement, and the photosensitive ink in the non-nickel-gold immersion treatment area is removed by an organic film-removing solution.

10. The method for preparing a PCB printed circuit board according to claim 1, characterized in that: The gong plate specifically divides the PCB substrate into PCB unit boards.

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