SMT flux is a liquid flux used for wave soldering during plug-in processing. Its function is to better help circuit components to achieve soldering. The quality of flux will also affect the quality of soldering to a certain extent, and most of the SMT workshops use solder paste. Therefore, in addition to the selection of flux, you should not buy it blindly. It must be determined according to the soldering product, equipment and customer requirements. The flux must be tested. Let's learn about the inspection method of flux in the following Sanjing belts:

①Water extraction resistivity test: This method is mainly to test the ionic characteristics of the flux. The test method is stipulated in the American Circuit Interconnection and Carrier Standard QQS-571 and other standards. Inactive rosin (R) and moderately active rosin flux (RMA) water extraction resistivity should not be less than 10000cm, and the water of active flux The extraction resistivity must be less than 100000cm, which cannot be used for military SMA and other circuit components with high reliability requirements.

②Copper mirror test: This method is to test the flux activity through the effect of the flux on the thin copper layer coated on the glass substrate. For example, QQ-S571 stipulates that for R and RMA fluxes, regardless of the test results of the extraction resistivity, if the activity of the copper coating on the copper mirror is removed, it will be unqualified.

③ Specific gravity test: This method is mainly to test the concentration of flux. In wave soldering and other processes, the specific gravity of flux is affected by its solvent evaporation and the amount of SMA soldering. Generally, it is necessary to track and monitor and adjust in time during the process to keep the flux at the set specific gravity and ensure the smooth progress of the soldering process. This method often adopts timed sampling and measurement with a hydrometer. It can also be carried out automatically by connecting an automatic flux specific gravity detection system.

④Color test: This method can show the chemical stability of the flux and the deterioration caused by factors such as exposure, heating and service life. Colorimetric agent test is a common method for testing. If you have rich experience, you can directly use visual inspection.

The above is about the content of SMT flux detection method, I hope it can be helpful to everyone!