Method for coating bottom of component with conformal coating

Abstract

The invention discloses a method for coating the bottom of a component with conformal coating. The method comprises the following steps: preparing the conformal coating according to the formula of the conformal coating; the printed board with the component is placed upwards, and three-proofing paint is dispensed at the gap between the component and the printed board along the periphery of the component, so that the three-proofing paint completely covers and shields the gap between the component and the printed board; a trumpet-shaped rubber nozzle covers an air exhaust hole in the back face of the printed board, the air exhaust hole directly faces the bottom of the component, an air exhaust device is started, the air exhaust device is connected with the trumpet-shaped rubber nozzle through an air exhaust pipeline, and conformal coating on the periphery of the component is pushed by air pressure to flow into the bottom of the component; after extracting for a period of time, closing the air extractor, and taking down the trumpet-shaped rubber nozzle from the printed board; and curing the conformal coating. According to the scheme, the problem that the bottom of a wide component is difficult to coat with conformal coating can be solved.

Description

Technical Field

[0001] This invention relates to the technical field of electronic assembly, and in particular to a method for coating the bottom of components with conformal coating. Background Technology

[0002] Conformal coating is a special protective coating applied to electronic circuit boards to enhance the overall performance of electronic products, including moisture resistance, mildew resistance, and salt spray resistance, to adapt to various working environments. To ensure the performance and shelf life of electronic and electrical products, protective coating treatment is necessary. Currently, there are three main methods for applying conformal coating: spraying, brushing, and dipping. Spraying involves atomizing the conformal coating using a nozzle and applying it to the product surface. Brushing involves applying liquid conformal coating to the product surface using tools such as brushes. Dipping involves immersing the product in conformal coating; after removal, the coating forms a layer on the product surface.

[0003] According to GB / T 38342 standard, the mounting height of radial components is 0.75mm~3.2mm. For relatively large radial components, the main disadvantage of spray coating is that the conformal coating is difficult to apply to the gaps at the bottom of the component. The main disadvantage of brush coating is uneven coating, easy missed areas, and difficulty in controlling the coating area. The main disadvantage of dip coating is the thick coating thickness, which easily leads to conformal coating buildup, and it cannot be used for areas that cannot be coated, thus limiting its application. Summary of the Invention

[0004] This invention provides a method for coating the bottom of components with conformal coating, aiming to solve the problem that it is difficult to coat the bottom of large components with conformal coating.

[0005] Firstly, a method for coating the bottom of components with conformal coating is provided, including: Prepare the conformal coating according to the formula; Place the printed circuit board containing the components face up, and apply conformal coating around the components to the gaps between the components and the printed circuit board, so that the conformal coating completely covers and conceals the gaps between the components and the printed circuit board. Place the horn-shaped rubber nozzle over the air extraction hole on the back of the printed circuit board, with the air extraction hole facing the bottom of the component. Activate the air extraction device. The air extraction device is connected to the horn-shaped rubber nozzle through the air extraction pipe, so that the conformal coating around the component is pushed into the bottom of the component by the air pressure. After a period of extraction, turn off the suction device and remove the horn-shaped rubber nozzle from the printed circuit board. Curing of the conformal coating.

[0006] In conjunction with the first aspect, in some implementations of the first aspect, the conformal coating formula is: 7385 polyurethane clear varnish: 7312 polyurethane curing agent: butyl acetate = 6:1:4.

[0007] In conjunction with the first aspect, in some implementations of the first aspect, the conformal coating is tested according to GB / T 1723 "Determination of viscosity of coatings".

[0008] In conjunction with the first aspect, in some implementations of the first aspect, the viscosity of the conformal coating is 16~20s.

[0009] In conjunction with the first aspect, in some implementations of the first aspect, the pumping capacity of the pumping device is set to 0.5~1L / s.

[0010] In conjunction with the first aspect, in some implementations of the first aspect, during the evacuation process, according to the requirements of coating area, thickness and coating area and thickness stability, the conformal coating dropper continues to move along the periphery of the component at a uniform speed while uniformly extruding the conformal coating, so that the conformal coating around the component is pushed by air pressure into the bottom of the component.

[0011] In conjunction with the first aspect, in some implementations of the first aspect, before evacuation, one ring of conformal coating is applied around the component, and during the evacuation process, three rings of conformal coating are applied.

[0012] In conjunction with the first aspect, in some implementations of the first aspect, the conformal coating is applied by a conformal coating dropper, which is either a syringe or a glue cartridge.

[0013] In conjunction with the first aspect, in some implementations of the first aspect, the curing regime of the conformal coating is as follows: the temperature is set to 40~60℃, and the coating is cured for 3~5 hours.

[0014] Compared with the prior art, the solution provided by the present invention has at least the following beneficial technical effects: 1) By adjusting parameters such as the viscosity of the conformal coating, the amount of conformal coating droplets, and the air extraction rate, the area and thickness of the conformal coating flowing to the bottom of the component can be controlled. 2) It is easy to operate, the tools are widely available, and it can be operated manually; 3) Compared to spraying or brushing, the extraction method can effectively control the coating area around the component; 4) By designing a track or platform for placing printed circuit board components, and installing conformal coating droppers, horn-shaped rubber nozzles, and air extraction pipes on a robotic arm, the method of this invention can be extended to automated equipment operation. Attached Figure Description

[0015] Figure 1 This is a schematic diagram illustrating the operation according to the method of the present invention.

[0016] Figure 2 This is a flowchart of the operation according to the method of the present invention.

[0017] Figure labeling: 1-Component; 2-Conformal coating; 3-Printed circuit board; 4-Ejection port; 5-French-shaped rubber nozzle; 6-Ejection pipe; 7-Ejection device; 8-Conformal coating dropper. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0019] This invention provides a method for coating the bottom of components with conformal coating, such as... Figure 1 As shown. This method requires drilling a hole in the printed circuit board 3 below component 1 during the PCB design to serve as a vent hole 4. This method requires a venting device 7, a flared rubber nozzle 5, a venting pipe 6, and a conformal coating dropper 8.

[0020] The vent 4 serves as the venting interface at the bottom of component 1. The venting device 7 has a venting pipe 6, and a flared rubber nozzle 5 is connected to the end of the venting pipe 6. The rubber nozzle 5 is aligned with the vent 4, covering and enclosing the vent 4 to ensure a tight seal between the venting device 7 and the vent 4, thereby enhancing the venting effect.

[0021] The conformal coating dropper 8 is used to apply conformal coating 2. Tools such as syringes and glue cartridges can be used. The air extraction device 7 extracts air from the bottom area of ​​component 1 through the air extraction hole 4, creating an air pressure difference between the bottom and the surrounding area of ​​component 1. This air pressure difference pushes the conformal coating 2, which has been pre-applied or is being applied during the process, along the bottom of component 1 and the surface of the printed circuit board 3, achieving the effect of applying conformal coating 2.

[0022] The operation method of this invention is as follows: Step 1: Prepare the conformal coating according to the formula and measure its viscosity. The viscosity of the conformal coating can be measured according to GB / T 1723 "Determination of Viscosity of Coatings". The viscosity of the conformal coating should meet the requirements of the standard specifications or process requirements.

[0023] Step 2: Place the printed circuit board 3 containing component 1 face up, and apply conformal coating 2 around the perimeter of component 1 in the gap between component 1 and printed circuit board 3. Visually inspect around component 1 to ensure that conformal coating 2 completely covers and conceals the gap between component 1 and printed circuit board 3.

[0024] Step 3: Set or adjust the air extraction rate of the extraction device 7 in advance to meet the process requirements.

[0025] Step 4: Cover the vent 4 on the back of the printed circuit board 3 with the horn-shaped rubber nozzle 5, start the venting device 7, and visually observe that the conformal coating 2 around the component 1 is pushed into the bottom of the component 1 by the air pressure.

[0026] In some embodiments, depending on the requirements for coating area, thickness, and coating area and thickness stability, the conformal coating dropper 8 can continue to move along the periphery of the component 1 at a constant speed while uniformly extruding the conformal coating 2, and visually observe the conformal coating 2 being pushed into the bottom of the component 1 by air pressure.

[0027] Step 5: After a period of extraction, turn off the suction device 7 and remove the horn-shaped rubber nozzle 5 from the printed circuit board 3.

[0028] Step six: Curing the conformal coating according to the document requirements.

[0029] Example 1 (1) Prepare the conformal coating materials: 7385 polyurethane clear varnish, 7312 polyurethane curing agent, and butyl acetate. The conformal coating formula is: 7385 polyurethane clear varnish: 7312 polyurethane curing agent: butyl acetate = 6:1:4. Weigh 60g of polyurethane clear varnish, 10g of polyurethane curing agent, and 40g of butyl acetate according to the above ratio, and mix them.

[0030] (2) According to GB / T 1723 "Determination of viscosity of coatings", the viscosity of conformal coatings shall be determined using a Coat-4 viscometer and shall meet the range of 16~20s.

[0031] (3) Place the printed circuit board containing the components face up, use a syringe to draw a tube of conformal coating, and apply the conformal coating along the perimeter of the components to the gap between the components and the printed circuit board. Visually inspect around the components to ensure that the conformal coating completely covers and conceals the gap between the components and the printed circuit board.

[0032] (4) Set the pumping capacity of the pumping device to 0.5~1L / s.

[0033] (5) Place the horn-shaped rubber nozzle on the air extraction hole on the back of the printed circuit board, start the air extraction device, and visually observe that the conformal coating around the components is pushed into the bottom of the components by the air pressure.

[0034] (6) Take another tube of conformal coating and continue to move the conformal coating dropper around the component at a constant speed, squeezing out the conformal coating at a constant speed, and visually observe that the conformal coating is pushed into the bottom of the component by the air pressure. Repeat the above method to apply the conformal coating around the component 3 times.

[0035] (7) After the coating is complete, continue to extract for 30 seconds, turn off the vacuum device, and remove the horn-shaped rubber nozzle from the printed circuit board.

[0036] (8) Place the coated printed circuit board in a temperature-controlled oven and set the temperature to 50°C for 4 hours to cure.

[0037] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims of the present invention.

Claims

1. A method for coating the bottom of a component with conformal coating, characterized in that, include: Prepare the conformal coating according to the formula; Place the printed circuit board containing the components face up, and apply conformal coating around the components to the gaps between the components and the printed circuit board, so that the conformal coating completely covers and conceals the gaps between the components and the printed circuit board. Place the horn-shaped rubber nozzle over the air extraction hole on the back of the printed circuit board, with the air extraction hole facing the bottom of the component. Activate the air extraction device. The air extraction device is connected to the horn-shaped rubber nozzle through the air extraction pipe, so that the conformal coating around the component is pushed into the bottom of the component by the air pressure. After a period of extraction, turn off the suction device and remove the horn-shaped rubber nozzle from the printed circuit board. Curing of the conformal coating.

2. The method according to claim 1, characterized in that, The conformal coating formula is: 7385 polyurethane clear varnish: 7312 polyurethane curing agent: butyl acetate = 6:1:

4.

3. The method according to claim 1, characterized in that, The viscosity of the conformal coating was tested according to GB / T 1723 "Determination of Viscosity of Coatings".

4. The method according to claim 3, characterized in that, The viscosity of the conformal coating is 16~20s.

5. The method according to claim 1, characterized in that, The air extraction rate of the extraction device is set to 0.5~1L / s.

6. The method according to claim 1, characterized in that, During the evacuation process, based on the requirements for coating area, thickness, and stability of coating area and thickness, the conformal coating dropper continues to move along the periphery of the component at a uniform speed while simultaneously extruding the conformal coating, so that the conformal coating around the component is pushed by air pressure into the bottom of the component.

7. The method according to claim 6, characterized in that, Before evacuation, apply one ring of conformal coating around the components, and apply three rings of conformal coating during the evacuation process.

8. The method according to claim 1, characterized in that, Conformal paint is applied by dripping it through a conformal paint dropper, which can be either a syringe or a rubber tube.

9. The method according to claim 1, characterized in that, The curing process for conformal coating is as follows: set the temperature to 40~60℃ and bake for 3~5 hours for curing.

Images