If we are going to carry out the repair of a printed circuit board, or PCB, the first thing we must do is check that it does not have defective components that are affecting its correct functioning.
What are the processes to detect components that do not work?
There are two systems that are primarily used for detecting malfunctioning components.
ICT Circuit Test
The first is an in circuit test (ICT) where, for example, a populated printed circuit board (PCB) is tested, checking for shorts, opens, resistance, capacitance, and other basic quantities that will show if the assembly is in good state. This is done without powering the electronic board.
Functional test
After this we find the functional part, that in this the pcb board is fed, here, there is a risk that when feeding it, it will have some more problems. For this reason, the ICT is carried out first, which is the one used to detect misplaced components, or if there is a short circuit that could cause a functional failure, once this is done, it is confirmed that the electronic board works correctly.
What types of components are easiest to detect in the presence of a fault?
The easiest components to detect, if we are in the presence of a failure, are the passive ones. Regardless of whether or not they receive power, we can measure them and identify their functionality.
However, in the case of active components, until they are supplied with power, they do not start to work properly, which means that the component may contain some welding problem or, in its periphery, there may be something causing failure, which would result in failure of the electronic board circuit flow.
As we have mentioned before, sometimes the damage can not only be in the components but also in the board, therefore, it is important to do a thorough review of it, since a damage to the board, no matter how slight, can cause complex damage to the rest of the components.
What are the processes that have been used to clean electronic boards?
In today’s electronics industry, pcb boards are not cleaned. Years ago, electronic boards were soldered, and then, as a general rule, washed in cleaning machines very similar to a domestic washing machine, but much more sophisticated.
This is because the products that were used for welding, if left on the plate, could harm it, so they had to be removed. This was an expensive process, in addition to the fact that products called CFCs (chlorofluorocarbons) were used.
These are substances derived from saturated hydrocarbons obtained by replacing hydrogen atoms with chlorine and fluorine atoms, which are highly polluting and contributed to the creation of the hole in the ozone layer, which has led to prohibiting its use.
This redirected the industry to look for alternatives to avoid having to clean the electronic boards; among these new alternatives the “No Clean” technique emerged, which means, not to clean (referring to the fact of not having to clean the electronic boards) .
How are electronic boards cleaned today?
Currently the plates are not cleaned unless it is a repair that is carried out manually; in this case cleaning is required since small residues may remain after this. The cleaning is done locally, focused on the areas where said waste is found; it is not done in a general way as it was done in the past.
How to clean an electronic board before a repair?
The first thing we must do when cleaning our pcb board is to remove the dust; we can do this using compressed air. It is considered to be an aesthetic process rather than a functional one.
However, it is carried out to be able to carry out other processes in a more comfortable and precise way, in addition to avoiding long processes of searching for breakages or electronic failures.
The second thing is to check the components, because if we find any failure in a component (many of the components used in electronic assemblies are highly sensitive to static electricity.
Summary
If pcb boards are touched with fingers without measures for discharge to ground from electrical charges, then they pass to the circuits causing damage), it is best to replace it. It is in this replacement process that the plate really gets dirty, and this is where the cleaning process must be carried out.
This cleaning, as we have mentioned before, will be done locally with special solvents for this type of component. Isopropyl alcohol is one of the elements widely used to clean electronic boards.
Under these processes we will be able to generate an effective and clean repair, avoiding residues on our electronic board.
