Classification and Selection of Wave Soldering Fluxes

Wave soldering machines are a common type of PCB soldering equipment that makes soldered connections by placing electronic components and circuit boards (with flux pre-coated on the soldered areas of the boards) on waves of molten solder.

Wave soldering usually requires the use of flux to improve soldering quality and efficiency. Different types of fluxes have different properties and uses, so it is important to choose the right flux. This article will introduce the classification and selection of wave soldering flux.

1. No-clean flux

No-clean flux activity is low, the active agent content is limited, after welding part of the flux residue in the product and not enough to cause corrosion short circuit or open circuit. No-clean flux although the residue corrosion is not high, but some flux residue dryness is not enough to have a strong adhesion ability, adsorption and adhesion to solid particles in the environment, some particles with conductivity, and ultimately the formation of electrical pathways, resulting in failure.

2. Highly corrosive flux

Highly corrosive flux is highly corrosive, after welding residues must be thoroughly cleaned, otherwise there will be chemical corrosion failure. In order to facilitate cleaning, high activity flux active agent more inorganic acids, soluble in water (easy to clean), low activity flux active agent more organic acids or organic acid salts, generally insoluble in water, not easy to clean.

How to choose the right flux?

1. If the product needs to be cleaned, it is recommended to choose a water-cleaning flux, easy to clean. If you choose no-clean flux, the difficulty of cleaning after welding increases, you need to use a professional cleaning agent (mostly alkaline solution), and add temperature to enhance its ability to dissolve the chemical reaction of the agent, the cost increases quite a lot.

2. Select the flux suitable for wave soldering process, you need to determine the type and content of the active agent according to the soldering temperature and soldering time. Generally speaking, low-activity, no-rinse fluxes are suitable for most wave soldering applications.

3. If the product requires high solder quality and reliability, it is recommended to choose a high activity flux, but need to pay attention to the residue cleaning process and cost.

4. If the soldering material has an influence on the choice of flux, it is necessary to select the appropriate flux according to the characteristics of the material. For example, for copper substrates, it is recommended to use high activity flux, because the reaction between copper and tin is not stable.

Wave soldering flux residue after welding sometimes can not be cleaned: the use of organic solvents or water-based cleaning agent can not effectively remove the residue. This is because the wave soldering flux is heated after spraying, the activity is stimulated and remove part of the oxide layer, in contact with the tin wave flux instantly by the high-temperature tin wave impact and vaporization, if the PCB soldermask curing is incomplete, the vaporized flux will be drilled into the PCB soldermask layer, there is a phenomenon that can not be cleaned off.

The program to prevent such problems is the PCB incoming inspection “tin bleaching test”. For the problem board has appeared, because of its nature does not affect the function and reliability of the product, in principle, can be ignored, for the appearance of demanding products, you can use a hot air gun to heat the product, while heating and wiping clean, can be cleaned to a certain extent the board, but the eradication is extremely difficult.

Features of NeoDen Wave soldering machine

Feature

Heating Method:  Hot Wind

Cooling method:  Axial fan cooling

Transfer Direction:  Left→Right

Temperature Control:  PID+SSR

Machine Control:  Mitsubishi PLC+ Touch Screen

Flux tank capacity:  Max 5.2L

Spray Method:  Step Motor+ST-6

Specification