Cleaning technology of printed circuit board

- Sep 22, 2018-

Water-based cleaning

1.1 water-base cleaning processThe water-based cleaning process takes water as the cleaning medium. In order to improve the cleaning effect, a small amount of chemicals such as surfactants, washing auxiliaries and corrosion inhibitors can be added into the water (generally 2-10%).According to the specific conditions of pollution of different properties on the printed circuit board, additives in water-based cleaning agent can be used to make the cleaning more applicable scope.The water-based cleaning agent has a good dissolving effect on water-soluble dirt, and then combined with physical cleaning means such as heating, scrubbing, spraying, ultrasonic cleaning and so on, it can achieve better cleaning effect.Adding surfactant to the water-based cleaning agent can greatly reduce the surface tension of water, strengthen the penetration and spreading ability of water-based cleaning agent, and better penetrate into the gaps between tightly arranged electronic components, and clean the dirt infiltrating into the substrate of printed circuit board.The solubility of water and emulsion dispersion of surfactants can also be used to remove the residues of synthetic active flux, which can not only dissolve all kinds of water-soluble dirt, but also remove non-soluble dirt such as synthetic resin and fat.Saponifier is a chemical used to saponify organic acids, such as rosin acid and fatty acid in oil, in cleaning printed circuit boards when appropriate saponifier is added into rosin flux or water-based cleaning agent.This is a common ingredient in many flux and grease detergents used to clean printed circuit boards.Saponifier is usually alkaline inorganic matter such as sodium hydroxide, potassium hydroxide and other strong alkali, also may be alkaline organic matter such as monoethanolamine.Organic solvents and surfactant components are commonly used in commercial saponifiers to clean out residues that cannot be saponified.The saponifier may corrode the aluminum, zinc and other metals on the printed circuit board.Therefore, corrosion inhibitors should be added in the formula.However, it should be noted that the printed circuit board which is sensitive to alkaline substances should not be cleaned with water based cleaning agent containing saponifier.

2.1 semi-water-based cleaning agentOrganic solvent and surfactant are commonly used in the components of semi-water-based cleaning agent. For example, the first ec-7 semi-water-based cleaning agent used in PCB cleaning is composed of terpene hydrocarbon solvent and surfactant.Water is also present in most semi-water-based detergent formulations, but because of its high water content (5%-20%), the semi-water-based solvent is as transparent and uniform as the solvent cleaning agent.Different from general solvent cleaner, the boiling point of the organic solvent used in semi-water-base cleaner is relatively high, so the volatility is low and it is not necessary to clean in a closed environment like solvent cleaner, and in the cleaning process it is not necessary to regularly replace the cleaner simply to supplement the cleaning dose.Make clean the PCB with half a water-based cleaning agent with organic solvents are mainly terpene classes and petroleum hydrocarbon solvents, glycol ether, N - methyl ketone of pyrrolidine west, etc., when selecting solvent type should be based on printed circuit boards, electronic components and raw materials, such as pollution and help when welding type used in welding details such as the tiger.