Testing Methods and Standards for PCB Cleanliness

The high-frequency and high-speed operation of electronic products, the increase of PCB wiring density, and the miniaturization of chip pin spacing make the cleanliness of the PCB board higher and higher. The performance of a PCB circuit board is directly related to the specific amount of visible and invisible residue between pads and holes on all areas of the active circuit.

The main pollutants that may be exposed to in the production of integrated circuits are particulate impurities, inorganic ions, organic substances, microorganisms, and gas impurities. A survey shows that the proportion of product failure due to pollution is as high as about 60%, and the cleanliness is not good enough, which may lead to various failure problems such as poor wetting, cracking delamination, and CAF.

Today, we will talk about two cleanliness testing methods for PCB boards for your reference.

 

Various materials of printed circuit boards can easily cause ion residues during the cleaning process, which affects the functionality and reliability of electronic products.

The problem of ionic contamination is very common. The most common problems caused by ionic contamination are surface corrosion and crystal growth, which eventually cause a short circuit, and excessive current flows through the connector, causing the final damage to the electronic product. For the PCB circuit board, to ensure the reliability of the product, it is particularly important to monitor the degree of ionic contamination!

The way of ion residue generation: PCB board manufacturing, soldering process, manual operation or pollution in the atmosphere, etc.

Forms of ionic contamination: There are mainly 5 forms of contamination, including flux residues, ionized surfactants, ethanol, aminoethanol, and human sweat.

There are two test methods for PCB ionic cleanliness: (1) anion and cation test method; (2) sodium chloride equivalent method. In general, it is recommended to choose the anion and cation test method, the advantage is that this method can clearly understand the source of the pollutant.

 

(1) Anion and cation test is a method to analyze the pollution degree by the type and content of anions and cations and organic acids. The test results are generally expressed in ug/cm2. The advantage of this method is that the residual species and content of each ion can be known in great detail.

Sample requirements: In order not to affect the accuracy of the test results, the surface area of the sample is generally required to be greater than 100cm2, and the sample needs to be sealed and packaged to prevent secondary pollution.

(2) Sodium chloride equivalent method is to use ultra-pure extraction solution to remove residues left from the process from electronic components. The measurement of cleanliness results is based on conductivity or resistivity.

The disadvantage of this method compared to the anion-cation method is that the method cannot clearly know the type and content of ion pollution.

By testing the cleanliness and specifying its limit, the damage caused by particle wear can be greatly reduced, the product failure caused by the existence of impurity particles can be prevented, the operating life and reliability of the whole machine can be improved, and the damage to the whole machine can be reduced.

 

The effect of unknown particulate matter on the product:

(1) Contaminant particles on the surface of parts will affect the service life.

(2) Large-sized pollutant particles (damaging pollutant particles) will cause functional damage to the powertrain.

(3) Contaminant particles on the surface of parts will affect the running stability.

We can use the above standard methods to verify whether the cleanliness of PCB products meets the limit requirements of relevant industries, so as to inspect and control the quality of products.

PCB Quick is an experienced PCB product supplier. We have a professional production team and a comprehensive management system. We have carried out comprehensive quality control whether from PCB design, packaging, or export. Our products are also sold all over the world because of their excellent performance. If you are interested in our printed circuit boards, please contact us immediately!