Circuit board back-washing method

Abstract

The invention discloses a back washing method of a circuit board. The back washing method comprises the following steps: soaking the circuit board in a back washing tank containing alkali liquor; soaking the circuit board in a clear water tank; washing the circuit board by using a high-pressure water gun; the circuit board washed by the high-pressure water gun is subjected to over-developing washing within 1 h, and the developing speed is controlled to be 1 m / min. According to the back washing method of the circuit board provided by the invention, the copper surface quality of the solder mask back washing board is improved, and the product quality is improved.

Description

Technical Field

[0001] The invention relates to the technical field of printed circuit board manufacturing, and in particular to a circuit board stripping method. Background Art

[0002] PCB (Printed Circuit Board) solder mask refers to a layer of solder mask ink covering the PCB surface and / or exposed holes (which can be through holes or blind holes) to form a permanent electrical environment insulation and chemical corrosion resistance protective layer to prevent wire scratches and wire short circuits during welding. It also has moisture resistance, heat resistance, insulation and aesthetics.

[0003] As printed circuit boards develop towards high density and high reliability, in the production process of printed circuit boards, the solder mask process is prone to poor plugging or other quality problems, and it is necessary to rework the defective PCB products after solder masking to remove the solder mask ink. In the prior art, the circuit board will have a batch of copper surface discoloration problems after OSP. After analysis, the copper layer lattice of the circuit board that has been removed and washed is destroyed. Tracing back the solder mask removal and washing board that has not undergone OSP, the large copper surface generally has a foggy defect phenomenon. The foggy foreign matter on the copper surface of the board mainly comes from the solder mask process. This kind of defect causes components to fall off easily and solder joints to be cold when the circuit board is soldered, which cannot meet customer quality requirements.

[0004] In view of this, an object of the present invention is to provide a circuit board stripping method to improve the copper quality of the board surface. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a circuit board stripping method, which can improve the copper surface quality of the solder mask stripping board and improve the product quality.

[0006] The technical solution of the present invention is as follows:

[0007] A method for de-cleaning a circuit board comprises the following steps:

[0008] Step S1, soaking the circuit board in a stripping tank containing alkaline solution;

[0009] Step S2, soaking the circuit board in a clean water tank;

[0010] Step S3, flushing the circuit board with a high-pressure water gun;

[0011] Step S4, the circuit board rinsed with a high-pressure water gun is subjected to a developing rinse within 1 hour, and the developing speed is controlled to be 1 m / min.

[0012] Furthermore, the number of plates dewashed at a single time is controlled to be ≤60pnl.

[0013] Furthermore, when the plugging plate is immersed in the de-cleaning tank, an ultrasonic cleaning process is performed.

[0014] Furthermore, the mass concentration of the sodium hydroxide solution in the de-washing tank is 10-15%, and the temperature is 80-90°C.

[0015] Furthermore, the circuit board is immersed in the de-washing tank for 30-35 minutes, and immersed in the clean water tank for 15-20 minutes.

[0016] Compared with the prior art, the circuit board de-cleaning method provided by the present invention has the following beneficial effects:

[0017] The circuit board dewashing method provided by the present invention reasonably controls the residence time of the circuit board from dewashing to developing and rinsing to prevent the residual solution on the board surface from damaging the copper surface lattice, so that the copper surface of the board surface after developing and rinsing is normal and free of foggy organic matter. After the circuit board after dewashing is normally processed by solder mask pre-treatment → silk screen → pre-baking → exposure → development → text → post-baking, the copper surface under the solder mask layer is normal and free of discoloration, thereby improving product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 It is a diagram showing the board surface effects after development and rinsing at different residence times in the circuit board stripping method of the present invention. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention and to make the above-mentioned objects, features and advantages of the present invention more obvious and understandable, the specific implementation modes of the present invention are further described below.

[0021] It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as there is no conflict between them.

[0022] A method for de-cleaning a circuit board comprises the following steps:

[0023] Step S1, soaking the circuit board in a stripping tank containing alkaline solution;

[0024] The alkali solution in the backwash tank is a sodium hydroxide solution with a mass concentration of 10-15% and a temperature of 85±5°C. When the circuit board is not required to be a plug hole, the circuit board is directly immersed in the backwash tank for 30 minutes. When the circuit board is a plug hole board, the circuit board is immersed in a backwash tank with an ultrasonic device for 35 minutes. The ink cured in the hole is first immersed in the sodium hydroxide solution in the backwash tank. After being softened under the action of ultrasonic vibration, the ink in the hole is easier to remove.

[0025] Step S2, placing the circuit board in a clean water tank and soaking it for 20 minutes;

[0026] Step S3, flushing the circuit board with a high-pressure water gun to better remove the ink in the hole;

[0027] Step S4, the circuit board rinsed with a high-pressure water gun is subjected to a developing rinse within 1 hour, and the developing speed is controlled to be 1 m / min.

[0028] In the present invention, the number of de-washing plates per time is controlled to be ≤60pnl, which can improve the de-washing efficiency.

[0029] After the circuit board is washed, the residual solution on the board surface will corrode the copper surface of the circuit board for a long time, destroy the copper surface lattice, and affect the appearance of the board. The copper surface quality of the circuit board after the high-pressure water gun is different when it stays for different time for the development and washing. Figure 1 As shown in the figure, after 3 hours of development and rinsing after de-washing, the copper surface of the board becomes foggy ( Figure 1 a); After 2 hours of development and rinsing after de-washing, the copper surface of the board has a slight fogging phenomenon ( Figure 1 b); After the stripping and washing, the copper surface of the board is normal and there is no foggy organic matter ( Figure 1 c).

[0030] According to the circuit board stripping method provided by the present invention, after the stripping, the circuit board is normally processed through solder mask pre-treatment → silk screen printing → pre-baking → exposure → development → text → post-baking, and after the circuit board is processed through OSP process, the copper surface under the solder mask layer is normal and has no different color, thereby improving product quality.

[0031] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations made to these embodiments without departing from the principles and spirit of the present invention are still within the protection scope of the present invention.

Claims

1. A method for de-cleaning a circuit board, characterized in that: The steps include: Step S1, soaking the circuit board in a stripping tank containing alkaline solution; Step S2, soaking the circuit board in a clean water tank; Step S3, flushing the circuit board with a high-pressure water gun; Step S4, the circuit board rinsed with a high-pressure water gun is subjected to a developing rinse within 1 hour, and the developing speed is controlled to be 1 m / min.

2. The circuit board stripping method according to claim 1, characterized in that: The number of plates to be washed in a single cycle is controlled at ≤60pnl.

3. The circuit board stripping method according to claim 1, characterized in that: When the plug hole plate is immersed in the de-cleaning tank, an ultrasonic cleaning process is implemented.

4. The circuit board stripping method according to claim 1, characterized in that: The mass concentration of the sodium hydroxide solution in the de-washing tank is 10-15%, and the temperature is 80-90°C.

5. The circuit board stripping method according to claim 4, characterized in that: The circuit board is immersed in the de-washing tank for 30-35 minutes and in the clean water tank for 15-20 minutes.

Images