Dispenser Does Double Duty for Printed Circuit Assembly

Robots and appliance doors — Computrol applies a conformal coating and a potting compound to a printed circuit assembly with the FCS300-ES (left) and MV500 spray valves, respectively. Photo courtesy Precision Valve & Automation

Computrol Inc. provides mid- to low-volume, high-mix electronic manufacturing services to OEMs around the world. From its manufacturing facilities in Meridian, ID, and Orem, UT, the company serves military, medical, aerospace, broadcast and general-industry customers.

In early 2012, Computrol faced a material-dispensing challenge at its Idaho facility. Specifically, a customer’s new printed circuit assembly (PCA) required a conformal coating in several areas, and epoxy potting in one area.

Because the potting application involved precise and repeatable placement of a micro-shot (0.0522-cc), Computrol knew the material could not be applied manually. At the same time, the company did not want to buy separate machines to apply the coating and potting.

So Computrol met with Precision Valve & Automation (PVA), one of its suppliers, to discuss automated, dual-function dispensing systems. PVA recommended a customized PVA650 system, which performs both applications in one workcell.

“The machine greatly reduces the amount of prep time required for conformal coating,” says James Spencer, manufacturing process engineer for Computrol. “It saves time and [provides] accuracy and repeatability, allowing us to increase throughput and get finished product into our customers’ hands quicker.”

The custom system features a servo-driven, three-axis robotic platform with encoders and ballscrew slides on all axes. It is compact but has a high payload capacity of 25 pounds. Each encoder has a resolution of 5 microns and provides feedback to ensure repeatability within 25 microns.

The conformal coating is applied with an FCS300-ES spray valve. An FC100 needle valve ensures edge definition. For potting, an MV500 positive-displacement metering valve is used.

System operators calibrate the valve needles to avoid dispensing head offsets. The conformal coating is dispensed from a 10-gallon pressure tank, and the potting material from a 5-gallon pail pump. Both containers feature low-level sensors.

Computrol really likes that the PVA650 offers a variety of valve mount configurations. By installing multiple valves on the platform, the company can process several assemblies simultaneously, apply more than one material or use multiple application heads.

System work area measures 459 by 459 by 101 millimeters. Maximum speed in any axis is 700 millimeters per second. Maximum acceleration is 1 g.

Other features include a chain conveyor and a camera. The conveyor has pin locators that stabilize the PCA pallet. The camera provides operators with an overhead image of the work area to teach paths of motion. It features memory channels and a programmable interface that permits coordination with external devices such as light sources.

For more information on dual-function dispensing systems, call 518-371-2684 or visit www.pva.net.

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