How to evaluate the effectiveness of cleaning PCBA circuit boards

The purpose of cleaning printed circuit boards is to remove conductive particles, flux, dust and other residues, achieve insulation, prevent poor contact, prevent poor contact of contact feet during path testing, prevent corrosion, etc. Therefore, the evaluation of PCBA cleaning is particularly important, which directly affects the quality of PCBA after cleaning. Therefore, this article evaluates and analyzes the effectiveness of PCBA cleaning as follows.

(1) Reliability evaluation

It is necessary to pre evaluate the reliability of printed circuit boards after cleaning when citing cleaning techniques and equipment.

We will use a reliability testing specific test printed circuit board for insulation testing evaluation, and use a pressure furnace for accelerated testing in terms of environment.

(2) Impact on components

Electronic components have a certain compatibility with cleaning agents. Various different test components or materials are selected for cleaning tests and pre evaluation is carried out. Especially for resin based electronic components, discoloration or expansion may occur due to the action of cleaning agents, printed text may fall off, water may seep into the components, and water accumulation during component installation should be carefully evaluated.

During the drying stage using hot air heating, due to the thermal stress on the components, it is necessary to confirm the heat distribution on the surface of the components through inspection.

During the drying stage using hot air heating, due to the thermal stress on the components, it is necessary to confirm the heat distribution on the surface of the components through inspection.

Common evaluation test methods:

When determining the specific specifications of each cleaning process, a comprehensive evaluation of the above issues must be conducted. The commonly used evaluation test methods are as follows:

① Visual inspection items can be directly visual, microscopic, or ultraviolet visual. By observing and determining the target of interest through visual inspection, PCBA can be evaluated for foreign objects or types of foreign objects.

② Ionic residue extraction test items generally use dynamic or washing methods, including ion radiation cameras or ohmmeters. At present, the quality of assembled boards is often evaluated based on the US military standard MIL-P-28809 after cleaning.

③ The electrical inspection and evaluation test project mainly involves testing insulation resistance and conductivity, which can refer to the Japanese industrial standard JISC5012.

④ The moisture resistance test items are environmental tests, mainly including constant test, cyclic test, pressure pot test, etc.

⑤ The solvent resistance test project for electronic components mainly tests the compatibility of components and the printing strength of characters. The main content is to carry out cleaning under specified operating conditions, evaluate whether there is color change and blistering, and pay attention to whether the printed or printed characters have faded or disappeared.