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 inFIGURES 2and3, 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).
The PCBAA is ramping up efforts to secure funding for R&D and capacity in the US.
What constitutes the printed circuit board industry? And how much, if any, investment should the US government allocate toward ensuring its technological and capacity capabilities?
These are among the questions David Schild is tackling every day. Schild is executive director of the Printed Circuit Board Association of America, which was founded in 2021 to advance US domestic production of PCBs and base materials. The organization is made up of corporate members of all sizes and includes fabricators, assemblers and suppliers.
Schild addressed questions about public and private investment, how governments can help create "demand signals," and the PCBAA's annual meeting with PCEA for the PCB Chat podcast in late July. The following transcript has been lightly edited for clarity and length.
The unstructured evolution of integrated circuit package technology (and its consequences).
I purchased my first "integrated circuit" around 1957, which was roughly a year before Jack Kilby is credited with inventing the IC. In appearance, it was a paper phenolic PCB with six discrete transistors in TO-cans and a few axial-leaded resistors and capacitors soldered on one side. If one can stretch their thinking just a bit, however, one can see the truth of the suggestion that it was arguably an "integrated circuit." The fact that Kilby was working at Centralab in Milwaukee, a ceramic circuit maker, immediately before heading to Texas Instruments for his new job was fortuitous. I have long assumed it influenced his invention. Around the same time, the IC's recognized co-inventor, Robert Noyce, took the idea a step further and showed how transistors and interconnections could be built on silicon wafer, which remains the primary method used today – featuring sizes a few orders of magnitude smaller and significantly increased material sets to embrace many new semiconductor materials in addition to silicon.