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Time of issue:2020-07-15 00:00:00
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The main factors affecting PCBA processing and cleaning

  • Categories:FAQ
  • Author:SAJ
  • Origin:
  • Time of issue:2021-07-05
  • Views:0

(Summary description)In a PCBA patch processing plant, in order to make the cleaning of printed circuit components proceed smoothly and achieve good results, in addition to understanding the cleaning mechanism, cleaning agent and cleaning method, it is also necessary to understand the main factors that affect the cleaning effect, such as PCB The design, the type and arrangement of the components, the welding process parameters, the type of flux, the residence time after welding and the parameters of solvent spraying. Below we will introduce these influencing factors in turn.
1. PCB design
In the case of wave soldering, the flux will flow to the upper surface of the SMA or under the SMD on the upper surface of the SMA through the plated through holes arranged under the components, which will bring difficulties to cleaning. Therefore, it is necessary to avoid setting plated through...

The main factors affecting PCBA processing and cleaning

(Summary description)In a PCBA patch processing plant, in order to make the cleaning of printed circuit components proceed smoothly and achieve good results, in addition to understanding the cleaning mechanism, cleaning agent and cleaning method, it is also necessary to understand the main factors that affect the cleaning effect, such as PCB The design, the type and arrangement of the components, the welding process parameters, the type of flux, the residence time after welding and the parameters of solvent spraying. Below we will introduce these influencing factors in turn.
1. PCB design
In the case of wave soldering, the flux will flow to the upper surface of the SMA or under the SMD on the upper surface of the SMA through the plated through holes arranged under the components, which will bring difficulties to cleaning. Therefore, it is necessary to avoid setting plated through...

  • Categories:FAQ
  • Author:SAJ
  • Origin:
  • Time of issue:2021-07-05
  • Views:0
Information

In a PCBA patch processing plant, in order to make the cleaning of printed circuit components proceed smoothly and achieve good results, in addition to understanding the cleaning mechanism, cleaning agent and cleaning method, it is also necessary to understand the main factors that affect the cleaning effect, such as PCB The design, the type and arrangement of the components, the welding process parameters, the type of flux, the residence time after welding and the parameters of solvent spraying. Below we will introduce these influencing factors in turn.

 

1. PCB design

 

In the case of wave soldering, the flux will flow to the upper surface of the SMA or under the SMD on the upper surface of the SMA through the plated through holes arranged under the components, which will bring difficulties to cleaning. Therefore, it is necessary to avoid setting plated through holes under the components during PCB design. Secondly, when wave soldering is used, the thinner substrate must be strengthened with ribs or plates to increase the resistance to deformation, and this reinforced structure will block the flux and is difficult to remove during cleaning. Therefore, the thickness and width of the PCB should match each other.

 

2. Component type and arrangement

 

 

With the development of miniaturization and thinning of components, the distance between components and PCB is getting smaller and smaller, which makes it more and more difficult to remove flux residue from SMA. For example, when cleaning after welding, complex components such as SOIC, OFP, and PLCC will prevent the penetration and replacement of cleaning solvents. When the surface area of the SMD increases, the SMD has leads on all four sides, and the lead center spacing decreases, the post-weld cleaning operation becomes more difficult. Therefore, the arrangement of components affects the cleanability of the SMA in terms of the extension direction of the component leads and the orientation of the components, and has a great influence on the flow speed, uniformity and flow of the cleaning solvent passing under the components.

 

3. Flux type

 

The type of flux is the main factor that affects the cleaning of SMA after welding. As the percentage of solids in the flux and flux activity increase, it becomes more difficult to clean flux residues. Therefore, SMA must comprehensively consider the required cleanliness level of the components and the cleaning process that can meet this level when selecting fluxes for welding.

 

4. Reflow welding process and residence time after welding

 

The effect of reflow soldering process on cleaning is mainly manifested in the temperature and residence time of preheating and reflow heating. The temperature of reflow heating is the rationality of the reflow heating curve. If the reflow heating curve is unreasonable and the SMA will overheat, it will cause the flux to deteriorate and it will be difficult to clean the residual flux. The residence time after welding refers to the residence time before the components enter the cleaning process after welding, that is, the process residence time. During this time, the flux residue will gradually harden so that it cannot be cleaned off. Therefore, the residence time after welding should be as short as possible. For a specific SMA, the maximum allowable residence time must be determined according to the manufacturing process and the type of flux.

 

5. Spray pressure and speed

 

In order to improve cleaning efficiency and cleaning quality, on the basis of static solvent or steam cleaning, spray scouring is mostly used. The use of high-density solvents and high-speed spraying can make the pollutant particles subject to large forces and easy to be removed. However, when the solvent is selected, the density of the solvent will become a non-adjustable parameter, and the only adjustable parameter left is the spray speed of the solvent.

 

The above are the main factors that affect PCBA processing and cleaning. Do you understand?

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