Printed Circuit Design & Fab Online Magazine - Features

Features

Conventional wisdom regarding via count is wrong. Here’s the proof.

Conventional wisdom has suggested:

The cross-sectional area of a via should have at least the same cross-sectional area as the conductor or be larger than the conductor coming into it. If the via has less cross-sectional area than the conductor, then multiple vias can be used to maintain the same cross-sectional area as the conductor. (IPC-2152, page 26, Note 1)

In other words, if the conducting cross-sectional area of the trace (width * thickness) is n times greater than the conducting cross-sectional area of the via, then we need n vias. Almost the entire industry believed this, including those of us at UltraCAD, until Johannes Adam and I began publishing our research results (Note 2).

If a recession is indeed ahead, Wally Rhines thinks the PCB design software industry is a “great place to hide.”

The figure tells the story: sales of printed circuit board design software set yet another record in the fourth quarter. The data, tracked by the ESD Alliance (part of Semiconductor Equipment and Materials International), tell a remarkable tale of growth. The industry has experienced just three year-over-year down quarters over the past decade.

Ryann Howard As the booths are rolled up and the last coffee cup is cleared from the Boxboro Regency, I find myself reflecting on my first PCB East – equal parts conference, class reunion and boot camp in the best possible way.

Fabrication-aware simulations to aid PCB design success.

As engineers design printed circuit boards (PCBs) to operate at higher data rates, the system’s signal integrity becomes increasingly sensitive to the variation in the fabrication process. A practical design is a software-defined design that includes realistic fabrication variation.

Typically, the PCB material properties in electronic design automation (EDA) software have default values. These ideal values for the material properties and PCB cross-sectional geometry are often called the as-designed values. On the other hand, after fabrication, the as-fabricated properties are the measurable numbers and dimensions from a physical board.

Higher layer count boards with mechanically drilled blind or buried vias may be built separately, then laminated together.

Sequential lamination is a fundamental manufacturing technique in an era of modern PCB fabrication and is a concept that must be especially understood when manufacturing high-density interconnect (HDI) PCBs with blind and buried vias.

Consider return loss and insertion loss – but don’t stop there.

Material selection for high-speed printed circuit board design is one of the most common instances where a PCB becomes overengineered. Many of the high-speed PCB design guidelines available on the internet provide generalized recommendations and suggest advanced materials that may not always be necessary for digital systems. In fact, many high-speed PCB products are manufactured using less advanced, moderate-loss FR-4 material.