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Time of issue:2020-07-15 00:00:00
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Small home pcba small class explanation: board circuit from China manufacturer's compatible design knowledge!
Small
Choose a reasonable wire width. The impact interference caused by the transient current on the printed lines of the PCB board circuit from China manufacturer is mainly caused by the inductance of the printed wires. Therefore, the inductance of the printed wires should be minimized.
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Choose a reasonable wire width. The impact interference caused by the transient current on the printed lines of the PCB board circuit from China manufacturer is mainly caused by the inductance of the printed wires. Therefore, the inductance of the printed wires should be minimized.
SMT patch dispensing process control
SMT

100000 clean workshop, as the name suggests, generally speaking, the production environment of the workshop should be very clean and tidy, which is the most basic element for general production plants. Below, we will introduce 100000 clean workshop in detail.

 

The whole vehicle room is clean and clean with complete electrostatic protection. It is equipped with central air conditioning in the whole workshop to control the cleanliness, temperature and humidity of the air contacted by the products, so that the patches can be produced, manufactured and tested in a good environment space, so as to improve the product quality.

 



 

However, since it is called a 100000 level clean workshop, the environmental parameters of the workshop must be strictly controlled

 



 

 

The first is the temperature and humidity control of the workshop. The temperature range is generally controlled between 18 ℃ and 28 ℃, and the humidity range is between 40% and 85%.

The second is the workshop air discharge and ventilation frequency. Fresh air volume ≥ 30 m3 / h / person, ventilation frequency ≥ 15 times / h.

Third, static pressure difference. Static pressure difference ≥ 5pa, static pressure difference ≥ 10Pa.

Fourth, the maximum allowable number of dust particles. ① 5 μ M: 3500000; ② ≥ 5 μ M: 20000.

Fifth, the number of floating / settling bacteria. ① The number of planktonic bacteria: ≤ 500 / m3; ② the number of settling bacteria: ≤ 10 / m3;

The last one is the test method. According to the implementation regulations of code for construction and acceptance of clean room (GB 50591-2010), check whether it meets the relevant national standards.

See more information

100000 clean workshop, as the name suggests, generally speaking, the production environment of the workshop should be very clean and tidy, which is the most basic element for general production plants. Below, we will introduce 100000 clean workshop in detail.

 

The whole vehicle room is clean and clean with complete electrostatic protection. It is equipped with central air conditioning in the whole workshop to control the cleanliness, temperature and humidity of the air contacted by the products, so that the patches can be produced, manufactured and tested in a good environment space, so as to improve the product quality.

 



 

However, since it is called a 100000 level clean workshop, the environmental parameters of the workshop must be strictly controlled

 



 

 

The first is the temperature and humidity control of the workshop. The temperature range is generally controlled between 18 ℃ and 28 ℃, and the humidity range is between 40% and 85%.

The second is the workshop air discharge and ventilation frequency. Fresh air volume ≥ 30 m3 / h / person, ventilation frequency ≥ 15 times / h.

Third, static pressure difference. Static pressure difference ≥ 5pa, static pressure difference ≥ 10Pa.

Fourth, the maximum allowable number of dust particles. ① 5 μ M: 3500000; ② ≥ 5 μ M: 20000.

Fifth, the number of floating / settling bacteria. ① The number of planktonic bacteria: ≤ 500 / m3; ② the number of settling bacteria: ≤ 10 / m3;

The last one is the test method. According to the implementation regulations of code for construction and acceptance of clean room (GB 50591-2010), check whether it meets the relevant national standards.

Cleaning technology of SMT surface assembly plate after welding
Cleaning
When it comes to SMT surface cleaning process, it is generally organic solvent cleaning or ultrasonic technology cleaning. Because of the high cleaning efficiency, it is widely used in SMT chip processing. Here are the differences between the two

 

Organic solvent cleaning: organic solvent is used for cleaning and rinsing. After cleaning, the organic solvent on the surface of the workpiece volatilizes rapidly without drying process. The cleaning mechanism is mainly dissolution. This method is suitable for cleaning water sensitive PCB and poor sealing of components.

 

Ultrasonic cleaning: ultrasonic technology can clean the pollutants at the bottom of components, between components and small gaps. It is suitable for post welding cleaning of SMT with high density, narrow spacing and serious pollution of surface assembly board. Because ultrasonic vibration can produce a large impact force, and has a certain ability to penetrate the components, it can penetrate the layers of the packaging material to enter the internal of the device, and damage the internal connection of the IC. It is generally not recommended for military products. Here is an introduction to the principle of ultrasonic cleaning

 



 

Under the action of ultrasonic wave, the cleaning agent forms pore structure and has diffusion effect. The cavity structure can produce a strong impact force, which can clean up the pollutants attached to the surface; ultrasonic vibration can make the liquid particles in the cleaning agent diffuse and accelerate the speed of the cleaning agent dissolving pollutants. In addition, the number of holes, the size of holes and the vibration force of cleaning agent are related to the vibration power and frequency of piezoelectric vibrator. The higher the density and size of the cavity, the higher the cleaning efficiency.

 

Finally, the selection conditions of cleaning agent are introduced

 

1. It has good wettability, so that the pollutants on the surface of SMT can be fully wetted and dissolved.

 

2. moderate capillary effect, small viscosity, can penetrate into the gap of components of the circuit board to be washed, and it is easy to discharge.

 

3. High density can slow down the volatilization of solvent.

 

4. High boiling point is favorable for vapor condensation. The cleaning agent with high boiling point has good safety, and the cleaning efficiency can be improved through continuous heating.

 

5. Solubility. Solubility is also known as kauranyl butanol value (KB value), which is the characteristic parameter of solvent for dissolving pollutants. The higher the KB value is, the stronger the ability of dissolving organic pollutants is.

 

6. Less corrosive. After cleaning, the characters and marks on the surface of components and printed circuit board can be kept clear.

7. Good safety, non-toxic and harmless, not flammable and explosive.

8. Low cost and less environmental pollution.
See more information
When it comes to SMT surface cleaning process, it is generally organic solvent cleaning or ultrasonic technology cleaning. Because of the high cleaning efficiency, it is widely used in SMT chip processing. Here are the differences between the two

 

Organic solvent cleaning: organic solvent is used for cleaning and rinsing. After cleaning, the organic solvent on the surface of the workpiece volatilizes rapidly without drying process. The cleaning mechanism is mainly dissolution. This method is suitable for cleaning water sensitive PCB and poor sealing of components.

 

Ultrasonic cleaning: ultrasonic technology can clean the pollutants at the bottom of components, between components and small gaps. It is suitable for post welding cleaning of SMT with high density, narrow spacing and serious pollution of surface assembly board. Because ultrasonic vibration can produce a large impact force, and has a certain ability to penetrate the components, it can penetrate the layers of the packaging material to enter the internal of the device, and damage the internal connection of the IC. It is generally not recommended for military products. Here is an introduction to the principle of ultrasonic cleaning

 



 

Under the action of ultrasonic wave, the cleaning agent forms pore structure and has diffusion effect. The cavity structure can produce a strong impact force, which can clean up the pollutants attached to the surface; ultrasonic vibration can make the liquid particles in the cleaning agent diffuse and accelerate the speed of the cleaning agent dissolving pollutants. In addition, the number of holes, the size of holes and the vibration force of cleaning agent are related to the vibration power and frequency of piezoelectric vibrator. The higher the density and size of the cavity, the higher the cleaning efficiency.

 

Finally, the selection conditions of cleaning agent are introduced

 

1. It has good wettability, so that the pollutants on the surface of SMT can be fully wetted and dissolved.

 

2. moderate capillary effect, small viscosity, can penetrate into the gap of components of the circuit board to be washed, and it is easy to discharge.

 

3. High density can slow down the volatilization of solvent.

 

4. High boiling point is favorable for vapor condensation. The cleaning agent with high boiling point has good safety, and the cleaning efficiency can be improved through continuous heating.

 

5. Solubility. Solubility is also known as kauranyl butanol value (KB value), which is the characteristic parameter of solvent for dissolving pollutants. The higher the KB value is, the stronger the ability of dissolving organic pollutants is.

 

6. Less corrosive. After cleaning, the characters and marks on the surface of components and printed circuit board can be kept clear.

7. Good safety, non-toxic and harmless, not flammable and explosive.

8. Low cost and less environmental pollution.
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