How clean circuit board
The traditional method of cleaning circuit board is to use organic solvents to clean, by CFC-113 and a small amount of ethanol (or isopropyl alcohol) consisting of a mixture of organic solvents on the residue of rosin flux has a very good cleaning ability.
But because we ban the CFC-113 has a destructive effect on the atmosphere ozone layer, the current optional non- ODS cleaning process, including water-based cleaning, semi-water-based cleaning, solvent cleaning, in addition to the cleaning process can be used without cleaning. In the end, which process to choose, should be based on electronic products and importance, the requirements of cleaning quality and the actual situation of the plant to decide.
1 Water-based cleaning circuit board
Water-based cleaning process
Water-based cleaning process is to use water as the cleaning medium, in order to that we improve the cleaning effect add to the water a small amount of surfactants, detergent additives, corrosion inhibitors and other chemicals (generally content in 2-10%). And can be for the specific circumstances of different nature of pollution on the printed circuit board, in the water-based cleaning agent additives, so that its cleaning a wider range of applications.Water-based cleaning agents have a good dissolving effect on water-soluble dirt, and then with heating, brushing, spraying and spraying, ultrasonic cleaning and other physical cleaning means, can achieve better cleaning results.
In the water-based cleaning agent to add surfactants can make the surface tension of water greatly reduced, so that the water-based cleaning agent penetration, spreading ability to strengthen, can better penetrate into the gaps between closely arranged electronic components, will penetrate into the printed circuit board substrate internal dirt cleaning. The use of water solubility and emulsification of surfactants to disperse the effect of us to remove synthetic active flux residues well, not only can a variety of water-soluble dirt dissolved to remove, but also synthetic resins, fats and other non-soluble dirt removed.
For the use of rosin-based flux or water-based cleaning
For the use of rosin-based flux or water-based cleaning cleaning agent to add the appropriate saponifier, saponifier (saponifier) is used in the cleaning of printed circuit boards with rosin in the rosin acid, fatty acids and other organic acids in grease saponification reaction to generate water-soluble fatty acid salts (soap) of chemical substances.This is a common ingredient in many cleaning fluxes and greases used to clean printed circuit boards.
Saponification agent is usually alkaline inorganic substances such as sodium hydroxide, potassium hydroxide and other strong bases, may also be alkaline organic substances such as monoethanolamine. In commercial saponifiers generally also contain organic solvents and surfactant components to clean and remove residues that can not saponification reaction. As the saponification agent may be on the printed circuit board aluminum, zinc and other metals to produce corrosion, especially in the cleaning temperature is relatively high, cleaning time is relatively long when it is easy to make corrosion increased. So we should add in the formula to the corrosion inhibitor. However, we should note that there are alkali-sensitive components of the PCB should not use water-based cleaning agents containing saponification agent cleaning.
2 Semi-aqueous cleaning circuit board
Semi-aqueous cleaning agent
In the components of the semi-aqueous cleaning agent generally have organic solvents and surfactants, such as the earliest use in the PCB cleaning EC-7 semi-aqueous cleaning agent,and terpene hydrocarbon solvent and surfactants compose them. In most of the semi-aqueous cleaning agent formula also contains water, but because of the water content of water (only 5%-20%), so from the outside of the semi-aqueous solvent and solvent cleaning agents are the same transparent, uniform solution.
Different from the general solvent cleaning agent is a semi-water-based cleaning agent using organic solvents with a high boiling point, so we don’t clean the low volatility in a close environment like solvent cleaning agent, and in the cleaning process do not have to often replace the cleaning agent only to properly replenish the cleaning dose. Otherwise, formulation of cleaning printed circuit board with semi-water-based cleaning agent with organic solvents are mainly terpene and petroleum hydrocarbon solvents, glycol ether, N-methyl-pyrrolidone, etc., the choice of solvent type should be based on the printed circuit board, electronic components and other raw materials such as pollution and welding flux type and other specific considerations.
3 Solvent cleaning process circuit board
Cleaning printed circuit boards using organic solvents
The use of organic solvents to clean the printed circuit board is the use of its dissolving effect on the dirt, in the elimination of CFC-113, TCA and other ODS cleaning agents, the current use of solvent cleaning agents are mainly HCFC, HFC, HFE and other fluorine solvents, in addition to hydrocarbon solvents, alcohol solvents, etc..
In order to improve the cleaning effect of fluorine solvents in which hydrocarbon solvents, alcohol solvents, etc. to form a mixture of solvents, some mixed solvents or azeotropic mixtures with constant boiling point (such as HCFC-141b-141b and methanol, HCFC-225 and ethanol with azeotropic mixtures of solvent cleaners).
As these fluorine solvents also have the advantage of non-flammable, and performance and CFC-113 is very similar, so the cleaning process and cleaning equipment basically do not need to change or only slightly adjusted.