Applying conformal coatings, either manually or automated, to printed circuit boards (PCBs) to protect them from solvents, moisture, dust, and other contaminants, can be arduous and costly, particularly when it involves masking. With any PCB, certain components could be compromised if exposed to coating, so tape or booth masking is manually applied to those areas prior to the coating process. After the coating, the mask needs to be removed by hand.
To help address this labor-, time-, and cost-intensive process, Precision Valve and Automation (PVA) of Halfmoon, NY, in 1994 developed an automated dispensing and conformal coating process that can be programmed to selectively and precisely coat only those areas on the PCB that require the protection. The result: masking is eliminated.
The precision of PVA's spray coating systems is crucial, with accuracies to within ±0.001 in. required. For example, their PVA750 is a programmable 3- to 4-axis, lean workcell platform that works inline or with manually fed coating systems. It has a large 19.68 x 19.68 x 3.94 in. work area that accommodates processing a variety of PCB sizes and configurations, and provides a positional resolution of ±0.0008 with ±0.0016 in. repeatability and travel speeds to 26.4 in./sec.
In the PVA conveyor system, one robot picks up the circuit board, another applies the coating, and a third sends the board to an oven for curing. The DMC-1530 and DMC-1540 controllers allow each robot to perform coordinated motion along a three-dimensional xyz path, and a rotational w path. In this exacting process, positional accuracy of ±0.001 in., uniformity of the coating, and high volume are critical.
To achieve this productivity, PVA incorporates Galil's DMC-1500 and DMC-2100 motion controllers to execute all control functions in all its systems, including its bench-type, selective, and automated coating and dispensing systems. These systems manage a range of dispense-and-apply operations via motion control, material curing using a controlled heat process via analog control, and circuit board trafficking through the work area via discrete control.
"Galil gives us lots of extended I/O so we don't need a separate PLC," says PVA controls engineer Joseph Baj. "The language is easy to learn and greatly simplifies programming. Galil has all the features we require: analog inputs, auxiliary encoders, and multitasking."
Baj also credits the flexible motion platform of the Galil controllers for enabling PVA systems to be quite versatile when it comes to fluid handling, whether dispensing silicones, acrylics, epoxy, or urethanes.
Galil's DMC-1500 is a high-performance, state-of-the-art motion controller designed for standalone operation. Using a 32-bit specialized microprocessor and a custom gate array, it provides digital signal processing (DSP) performance without sacrificing ease of use and cost effectiveness.
The DMC-2100 controller provides up to 8 axes of motion control, 64 points of digital I/O, and 8 analog inputs. It makes interfacing with robots on the production line easy by simply linking the controllers and I/O on Ethernet. PVA also uses Galil's IOC-7007 controller for extended I/O on Ethernet, allowing for more I/O without adding a separate PLC.
Jon Merrill, applications engineer at PVA, says the compatibility of the Galil controllers further contributed to their ease-of-use. "It's easy to switch between the DMC-1500 and the DMC-2100 because the same Galil programs run on both controllers. Galil's ActiveX controls also make it easier to develop applications."
