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Time of issue:2020-07-15 00:00:00
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Causes and solutions of white spots in PCBA processing

  • Categories:FAQ
  • Author:SAJ
  • Origin:
  • Time of issue:2021-07-12
  • Views:0

(Summary description)Today we are going to understand what is the leukoplakia that is often said in PCBA processing and why it occurs and the method to solve it.
Among PCBA processed products, some PCBA processed products may encounter white spots. White spots generally appear in the soldering process or post-soldering cleaning process, mainly manifested as white spots or white residues on or around the surface of the PCB, pins and solder joints. The components of the white spots may be crystalline rosin, rosin denatured substances, organic and Inorganic metal salts, group soldering flux, ...

Causes and solutions of white spots in PCBA processing

(Summary description)Today we are going to understand what is the leukoplakia that is often said in PCBA processing and why it occurs and the method to solve it.
Among PCBA processed products, some PCBA processed products may encounter white spots. White spots generally appear in the soldering process or post-soldering cleaning process, mainly manifested as white spots or white residues on or around the surface of the PCB, pins and solder joints. The components of the white spots may be crystalline rosin, rosin denatured substances, organic and Inorganic metal salts, group soldering flux, ...

  • Categories:FAQ
  • Author:SAJ
  • Origin:
  • Time of issue:2021-07-12
  • Views:0
Information

Today we are going to understand what is the leukoplakia that is often said in PCBA processing and why it occurs and the method to solve it.

 

Among PCBA processed products, some PCBA processed products may encounter white spots. White spots generally appear in the soldering process or post-soldering cleaning process, mainly manifested as white spots or white residues on or around the surface of the PCB, pins and solder joints. The components of the white spots may be crystalline rosin, rosin denatured substances, organic and Inorganic metal salts, group soldering flux, flux or cleaning agent and other chemical substances produced by high temperature welding, but most of them come from the chemical change of rosin or water-soluble acid in the soldering flux, resulting in relatively higher substances. Its original composition is more difficult to dissolve in cleaning agents.

 

 

White spot phenomenon occurs in both wave soldering and reflow soldering processes. The white spot composition is very complex and its cause is not easy to predict. Generally, relatively loose resin residues can be cleaned and removed after swelling and dissolving by selecting a combination of different solvents based on the principle of similar compatibility and solubility coefficient. However, organic acids will undergo metal saponification reactions with tin, lead and other metals and their metal oxides to form carboxylates, and the higher the temperature, the longer the time the more the formation. This type of hard metal salt cannot be removed by general solvents, so ultrasonics are needed to assist in cleaning. Therefore, the process can reduce the formation of such residues by lowering the temperature and shortening the time. In addition, the denaturation of the organic matter after soldering brings difficulties to the composition of the cleaning agent. In addition to the variety of the group flux and the chemical interference in the PCB production process, the intervention of certain solvents in the flux destroys the original surface quality of the group flux, making White spots are emerging one after another.

 

In view of the fact that there are many types of leukoplakia and will have a certain impact on the quality of PCBA processed products, it is necessary to find out the causes of different types of leukoplakia. So, what are the ways to avoid PCBA white spots?

 

First of all, the first one is to control the cleanliness of PCB and components; secondly, in the selection of flux or solder paste, low solid content or no-clean flux or solder paste should be selected; third, strengthen process control; fourth, prevent PCBA transfer Process pollution; Fifth, adopt clean new technology to avoid pollution to the environment.

 

The above is about the causes and solutions of leukoplakia in PCBA processing. I hope it can be helpful to everyone!

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