The following will introduce the hybrid and mixed dielectrics PCB in Multilayer PCB.Multilayer printedcircuit boards (PCBs) can provide many advantages to RF/microwave circuit designers in terms of achieving high functional density during a small size, while also improving reliability and cutting cost.
As some designers have found,the multiple layers needn’t be an equivalent dielectric materials: a growing number of RF/ microwave circuit designs are being implemented with hybrid multilayer PCBs, during which different materials are used among the layers. This enables the selection of materials to be tailored to the varied functions on the various layers of the PCB. Of course, there are some areas of concern when adopting such a design approach, and this text will provide an easy overview of those hybrid multilayer PCBs in terms of fabrication, electrical performance, and therefore the sorts of circuit materials that are suitable for hybrid multilayer PCBs.
One circuit material that’s used very often in high-frequency hybrid multilayer PCBs is FR-4, although it’s going to not be the foremost ideal choice for a few circuits. Low-cost FR-4 circuit materials are in use for a good range of circuits for many years . FR-4 is glass-reinforced epoxy laminate material.
Its performance is predictable and reliable, and it are often processed with basic fabrication methods. However, FR-4 exhibits a really high dissipation factor, which translates into high dielectric losses for circuits at microwave frequencies. due to its loss characteristics, FR-4 is usually not used for pure RF/microwave circuits, but has been utilized in some high-frequency hybrid multilayer PCBs forvarious reasons.
FR-4 is out there in standard grade and with high glass transition temperature (Tg), which is that the temperature at which the modulus of the fabric will change dramatically. Such temperature changes can impact the reliability of plated through holes (PTHs) through the laminate, as wont to interconnect different circuit layers during a multilayer PCB.
Some high-Tg FR-4 materials provide good stability with the processing temp eratures required for several circuit fabrication techniques, with relatively low coefficient of thermal expansion (CTE) in the z-axis permanently PTH reliability.