A design, equipment, process and materials methodological approach.

Electronics for automotive applications, as well as for other industries, are expected to reliably operate in harsh environments at a competitive cost. Advances in safety, communication and displays are driving miniaturization and integration of sub-devices onto the PCB assembly; e.g., cameras, sensors, and LEDs. Electrification trends are also leading to higher voltage requirements. In one example of a harsh environment application, automotive door and window control modules may have a critical circuit or component that is desired to function for a specified amount of time, even while submerged in water.

This paper describes an enabling technology to assist in the protection of critical functionality on PCB assemblies. 3-D-printed plastic retaining or "barrier" walls are formed to precisely control the location and height of a dispensed encapsulant in a region of the circuit that is sensitive to the environment. A case study was undertaken for the creation of 3-D-printed retaining walls, formed directly onto the surface of PCB substrates, without the need for separate parts, mold tools, mechanical or liquid fasteners, and complex manufacturing equipment. Also eliminated is the need to encapsulate or pot the entire PCB assembly, which adds additional complexity and cost. The encapsulant-filled retaining wall structure protects critical circuits from chemical, mechanical and electrical external factors such as moisture, fluids, gasses, particulate contamination, physical contact, or arcing in applications requiring high voltage. A 3-D model of the SIR test PCB having a representative retaining wall structure, surrounding an interdigitated test circuit, is shown in FIGURE 1. The retaining walls hold a liquid-dispensed encapsulant in place, at a predetermined height. In the absence of a retaining wall structure, as shown in FIGURES 2 and 3, an encapsulate can spread uncontrollably across the surface of the PCB (Figure 2), or result in insufficient height of the encapsulant, exposing electronics circuitry (Figure 3).

Compensation continues to rise among PCB designers.