Why should PCB be cleaned?

When troubleshooting non-functional or poorly performing circuits, engineers can usually run simulations or other analysis tools to consider the circuit from the schematic level. If these methods do not solve the problem, even the best engineers may be stumped, frustrated or confused. I have also experienced this pain. To avoid getting into a similar dead end, I will introduce a simple but very important tip: keep it clean!

What does that mean? This means that certain materials used during PCB assembly or modification can cause serious circuit functional problems if the PCB is not properly cleaned. One of the most common problems in such phenomena is flux.

Flux is a chemical agent used to assist in soldering components to the PCB. But it is regrettable that if it is not removed after soldering, the flux will deteriorate the surface insulation resistance of the PCB, which will cause serious degradation of the circuit performance in the process!
Flux contamination has a serious impact on the output performance of the bridge sensor. In the absence of cleaning or manual cleaning, the bridge sensor voltage never reaches the expected voltage of approximately VREF / 2, even after the one-hour settling time. In addition, uncleaned circuit boards also exhibit a large amount of external noise collection. After cleaning with an ultrasonic bath and completely drying, the voltage of the bridge sensor is stable as a rock.
In short, improper flux cleaning can cause severe performance degradation, especially in high-precision DC circuits. For all PCBs that are manually assembled or modified, be sure to use an ultrasonic bath (or similar method) to complete the final cleaning. After air-drying with an air compressor, PCBs assembled and cleaned at a slightly higher temperature can be used to remove any residual moisture. We usually bake at 70 ° C for 10 minutes.
This simple "keep clean" technique should help you significantly reduce the time spent troubleshooting and help you devote more time to designing excellent high-precision circuits!