Coating Of Circuit Board Flux
Coating Of Circuit Board Flux – Flux Spray – Cheersonic
The flux must be applied to the underside of the printed board in the most efficient and economical way possible. The flux coating should be uniform and completely cover the soldered parts. If the flux is used in excess, it will not only drip onto the preheater and cause a fire hazard, but also be a great waste and greatly increase the workload of cleaning the printed board components. Regardless of how the flux is applied, the excess flux should be scraped off with an air knife or adjustable applicator on the printed board passing through the flux slot.
In fact, the most widely used automatic soldering machines use one of the following methods to apply flux: wave, foam, brush, spray or dip. Among them, the wave-type and foam-type coating methods are the most commonly used, so they are discussed in more detail.
a. Foam type flux coating device The foam type flux coating device consists of a liquid storage tank and a long nozzle with a high liquid level, and there is a porous stone under the nozzle. A typical setup is to create foam peaks through nozzles called spray nozzles. Fill the flux pump with flux about two inches over the porous stone. Compressed air is passed into the porous stone, so that the foam peaks rush out of the spray port to meet the lower surface of the welded part. In order to prevent the foam flux from being polluted by oil and water in the gas path, a filter and an oil-water separator should be installed on the gas path. The pressure in the air circuit should be adjustable to control the air pressure and flow to the porous stone. Typically 3-5 pounds of pressure is sufficient. There should also be needle valves in the air circuit to precisely adjust the flow to control the flatness of the foam peaks. Using a foam-type flux coating device, the surface of the printed board can be coated with a thin and uniform layer of flux. This arrangement is more effective when the parts being welded have a large number of metallized holes. Obviously, in such a device, the use of the action of the foam punched out of the holes is the most efficient method.
b. Wave type flux applicator The wave type flux applicator consists of a pump and a nozzle similar to the foam type flux applicator. However, in this setup, the flux is drawn through the nozzle to form a stable flux wave. The part to be fluxed can pass through the top of the wave. This method cannot strictly control the amount of flux applied to the printed board, but it is suitable for mass production.
c. Flux spray method Flux spray method is another technique for coating flux on the surface of printed boards. It has the advantage of accurately controlling flux amount, uniformity and location, but it is dirty and requires frequent maintenance. The flux used in the operation should be a volatile type of solvent, which makes the flux expensive and difficult to control. Unless it is absolutely necessary to precisely control the flux deposition parameters by this method, a foam-type flux applicator is more attractive.
d. Flux brushing and dipping Brushing and dipping techniques are fairly common techniques and need no explanation. However, this technology is not suitable for high-speed or mass production.
Cheersonic’s ultrasonic sprayer is an alternative flux system for selective soldering machines. The ultrasonic spray system is designed to solve the main problems of most standard fluxes, such as spray and air pressure spray. The ultrasonic spray system will spray all flux without clogging, increasing accuracy, increasing production speed and reducing overspray.
Fully automatic multi-axis ultrasonic solder spray flux system with precise selective area flux function. Advanced dot programming capabilities; simply import an image of the PCB and highlight areas that require flux. Ideal for trays and PCBs with unnecessary flux. It has been proven to reduce flux consumption by up to 93%.
The fully automatic multi-axis ultrasonic solder spray flux system has advanced spray accuracy, and the maintenance amount is reduced by 95% compared with the traditional pressure spray flux. All fully automatic multi-axis ultrasonic solder spray flux systems have ultrasonic spray performance that is non-blocking, repeatable, and low-maintenance.
