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In a typical interconnect, there lie multiple places where capacitance plays a factor in the signal integrity. This includes the driver and receiver output/input capacitance, as well as the packages, vias, and the transmission lines. Failing to optimize these parameters can often lead to unwanted reflections, excessive radiated and or conducted emissions, and sometimes failure of components and systems.
Reflections can occur anytime there is an impedance mismatch on the line. Sources of mismatches are plentiful and include trace width changes, vias, stubs, reference plane changes, and even the so-called fiber weave effect. In this case, a trace can encounter a different dielectric constant depending on whether it is routed over glass or the epoxy resin in the dielectric material.
In this investigation, it is the capacitive contribution of the different components that are of interest, and how they affect the characteristic impedance the driver sees.
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Dr. John Parry, CEng, Mentor
When designing a PCB, thermal issues are often locked in at the point of selecting and laying out the chip package for the board. After that, only remedial actions are possible if the components are running too hot. Assumptions made about the uniformity of the airflow in these early design stages can mean a disaster for the commercial viability of a PCB if those assumptions are incorrect. A different approach is needed to improve reliability and to optimize board performance. Dr. John Parry of Mentor explains.
Patty Goldman, I-Connect007
IPC’s fall committee meetings were held in conjunction with SMTA International, as has been the case for several years now. Patty Goldman sat in on some subcommittee meetings, including one on laminates, where she met up with Ventec COO Mark Goodwin for a discussion on thermal management from a laminate supplier’s perspective.
Paul Taubman, Nine Dot Connects
In order to understand the current climate, we have to look at the division of labor that took place in electronic design about 40 years ago. The labor was divided into two processes, with the first being the design itself. This process was (and still is) owned by the electrical engineers. Though circuit design has changed, the methods for representing the circuit have not. Paul Taubman of Nine Dot Connects explains.