Argus Frequently Asked Questions

Frequently Asked Questions

How does the HVLP-heated gun work?

Does the heated gun have benefits in addition to reduced solvent usage?

How does the unit handle over-spray?

What is the expected LPISM efficiency?

Can the PC9524 spray materials other than LPISM?

How does the PC9524 apply a uniform coating with just one spray gun?

How does the PC9524 deal with LPISM in the barrels?

What is Argus International's experience with LPISM systems?

How does the HVLP-heated gun work?

HVLP stands for high-volume low-pressure, a type of spray gun that allows chemical coatings to be atomized into a fine spray through the use of air pressure. Typical HVLP systems require that the spray liquid be diluted with a compatible solvent to a viscosity low enough to allow proper atomization. For example, to spray liquid photoimageable solder mask (LPISM) in a typical, unheated HVLP gun, approximately 40% additional solvent by weight is usually required.

The Argus PC9524 Spray Unit, however, does not use a typical spray gun. The heated gun technology developed by Argus International significantly reduces solvent usage during spray, providing economic, safety, and environmental benefits. This technology, which heats both the LPISM and the atomizing air at the point of spray, causes a drop in LPISM viscosity just long enough to allow proper atomization without the use of excessive amounts of solvent.

Does the heated gun have benefits in addition to reduced solvent usage?

Heated spray gun technology has improved the ability of HVLP systems to encapsulate traces, because the LPISM returns to room temperature and higher viscosity before it strikes the PCB. The heated gun also reduces LPISM usage by allowing thinner coatings to adequately cover higher circuit traces.

Because the heated gun requires less solvent in the LPISM, tack-dry times are significantly reduced; if the PC9724 IR Tack-Dry Oven is used in conjunction with the PC9524 Spray Unit, tack-dry time may be reduced to as little as 3 minutes.

How does the unit handle over-spray?

Touch screen input of board dimensions and photocell detection of board position allow the operator to control the spray pattern and coverage of the desired area of the PCB, thus minimizing over-spray.

The exhaust system, which is designed to remove solvent vapors and any over-spray from the low-volume spray chamber, maintains straight-line flow in the direction of spray. This configuration combines efficiency of operation with reduced equipment size and cost.

Any LPISM which adheres to the edge-contact conveyor is continuously removed by an automatic cleaning system.

What is the expected LPISM efficiency?

Typical spray operation will provide 140 to 150 square feet of a 1 mil thick dry coating per kilogram of LPISM; this easily equals or exceeds the efficiency and economy of other methods of application. Because of the heated spray gun technology, this 1 mil coating will adequately cover much higher traces than a coating produced by other methods, yielding additional economy of operation. For example, 5-7 mil high traces have been encapsulated with half the dry thickness coating required with silk screen systems.

Can the PC9524 spray materials other than LPISM?

In addition to LPISM, the PC9524 Spray Unit has been tested for use with photoimageable legend inks, primary image resists and photoimageable dielectric coatings. In the future, Argus expects to offer a system for inner-layer coating of liquid resists for production-volume processing. This system should allow major cost reduction in both raw materials and equipment, and will likely cause a shift away from dry film in primary image processing.

How does the PC9524 apply a uniform coating with just one spray gun?

The PC9524 Spray Unit uses a shuttle head that attains speeds of up to 155 feet per minute. This allows the single spray gun to sweep the width of the PCB while the board moves forward as little as half an inch. Because the spray pattern from the heated gun is approximately 3.5 inches wide, the entire PCB may receive as many as 7 coats of LPISM during the spray process. At typical conveyor speeds, the board will receive 4 coats of LPISM.

Simplicity of setup, speed of operation, and uniformity of performance all favor the use of a single spray gun system. This system is not subject to multiple gun spacing, placement, adjustment and pattern problems that can all lead to inconsistent coating thickness.

How does the PC9524 deal with LPISM in the barrels?

LPISM in the barrels is a significant problem in silk screen application methods. Because the silk screen squeegee forces LPISM into the holes, higher developer pressure is required to obtain clear holes.

Spray coating with the PC9524 does not result in significant amounts of LPISM in the barrels, as the mask is not forced into the holes as it is by the squeegee; therefore, lower developer pressure can be used, and process speed is improved. LPISM dams between fine pitch patterns are more easily held, under-cut during development is reduced, and the surface cosmetics are improved because proper developing procedure can be maintained.

What is Argus International's experience with LPISM systems?

The Argus Technical Service Laboratory is currently accumulating many LPISMs, with the objective of creating a databank of characteristics, operating parameters, and peculiarities. This information will be made available to customers. The Laboratory also demonstrates the PC9524 Spray Unit and the PC9724 IR Tack-Dry Oven, and processes sample boards for potential customers.

For installation, our Process Engineering Group will assign a process engineer to assist in physical location of the equipment, conduct initial start-up and train operating personnel at your facility. Continuing technical support, service, and parts supply are provided with the same dedication that has existed at Argus International for over 30 years.