How to Clean PCBA Boards Pollution？

Generally, the PCBA boards of electronic products has to go through the SMT+THT process, during which it has to go through wave soldering, reflow soldering, manual soldering and other welding processes. sources of pollution.

Contaminants are surface deposits, impurities, slag inclusions and adsorbed substances that reduce the chemical, physical or electrical properties of PCBA boards to unqualified levels. There are mainly the following aspects:

(1) The components that make up the PCBA boards, the pollution or oxidation of the PCB itself will cause the board surface pollution of the PCBA boards;

(2) During the manufacturing process of the PCBA boards, solder paste, solder, solder wire, etc. are used for welding, and the flux in it will produce residues during the welding process to form pollution on the board surface of the PCBA boards, which is the main pollution thing;

(3) There will be imprints during the manual soldering process, and some wave soldering claw footprints and soldering tray (fixture) marks will be produced during the wave soldering process. There may also be other types of pollutants on the surface of the PCBA boards to varying degrees, such as plugging Pore glue, residual glue of high temperature tape, hand marks and flying dust, etc.;

(4) Dust in the workplace, water and solvent vapor, smoke, tiny particles of organic matter, and charged particles caused by static electricity attached to the PCBA boards pollution.

Why Clean PCBA Boards?

In the past, people did not know enough about cleaning, mainly because the assembly density of PCBA boards of electronic products was not high, and they believed that flux residues were non-conductive and benign, and would not affect electrical performance. Today's PCBA boards design tend to be miniaturized, smaller devices, smaller pitches, pins and pads are getting closer, and the existing gaps are getting smaller and smaller, and pollutants may be stuck in the gaps. It means that if relatively small particles remain between the two pads, it may cause potential defects in the short circuit of the PCBA boards.

According to the research, according to the analysis and statistics of PCBA boards quality problems, the short circuit and open circuit caused by corrosion and electromigration account for 4% of the later use failure problems, which are one of the major killers of product reliability.

Pollution may directly or indirectly cause potential risks to the PCBA boards, such as the organic acid in the residue may cause corrosion to the PCBA boards; the electric ions in the residue may cause electrons to scatter during the electrification process because of the potential difference between the two pads. If it is moved, it may form a short circuit and make the PCBA boards invalid; the residue will affect the coating effect, which will cause the problem of inability to coat or poor coating; it may not be found temporarily, and the coating will appear after time and changes in ambient temperature. Cracks and warped skin can cause reliability problems.

It can be seen from the ever-growing PCBA boards product market that modern and future electronic products will become smaller and smaller, and the requirements for high performance and high reliability will be stronger than ever before. Thorough cleaning is a very important and highly technical work, which directly affects the working life and reliability of PCBA boards electronic products, and is also related to the protection of the environment and human health.

The PCBA boards cannot be cleaned casually, and strict requirements and precautions are required. The following is a brief explanation of the purpose, necessity and some precautions in the process of PCBA boards cleaning according to the PCBA boards cleaning rules.

The Purpose of PCBA Boards Cleaning

PCBA boards cleaning is a process of dissolving and removing soldering residues. The purpose of cleaning is to essentially prolong product life by ensuring good surface resistance and preventing leakage.

The necessity of PCBA Boards Cleaning

In the process of PCBA boards processing and production, solder paste and flux will produce residues during PCBA boards processing and welding. The residues contain various components: organic acids and decomposable ions. Ions residues on the pads will cause short circuits, and these residues are relatively dirty on the PCBA boards, which does not meet the customer's requirements for product cleanliness, so it is inevitable to clean the PCBA boards.

Precautions for PCBA Boards Cleaning

1. Timeliness, PCBA should be cleaned as soon as possible after solving

After the PCB board is assembled and soldered, it should be cleaned as soon as possible (because the flux residue will gradually harden over time and form corrosion products such as metal halide salts), and the residual flux, solder and other pollutants on the PCBA boards should be completely removed.

2. To prevent the intrusion of cleaning agents, bake and dry

When cleaning the PCBA boards, it is necessary to prevent harmful cleaning agents from intruding into the components that are not completely sealed, so as to avoid damage or potential damage to the components. After the PCBA boards assembly is cleaned, put it in an oven at 40-50°C and bake and dry for 20-30 minutes. Before the cleaned parts are dry, do not touch the components with bare hands.

3. Cleaning cannot damage the PCBA boards

Cleaning should not affect components, markings, solder joints and PCBA boards.

Thoroughly cleaning the PCBA boards are a very important and delicate work, which directly affects the working life and reliability of electronic products, and is also related to the protection of the environment and human health. It is necessary to re-understand and solve the problem of soldering cleaning from the perspective of the entire PCBA boards production process. The implementation of the cleaning plan must cooperate with the use of soldering materials such as flux, solder paste, and solder wire, and organic solvents, inorganic solvents, and their mixed solvents. Only by matching each other with water washing or no-cleaning can the residues be effectively removed, so that the cleanliness of PCBA boards can better meet customer requirements and ensure the quality of PCBA boards.

Get How to Clean PCBA Boards Pollution？

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