sandwich boards with additional internal layers of copper and insulation are called multilayer. PCBs can be single-sided (one layer of copper), double-sided (two HASL layers of copper on both sides of an insulating board), or multi-layered (outer and inner layers of copper alternating with insulating layers). Among the multi-layer PCBs, the most common are the four-layer
is an alternating current (AC) characteristic HASL that increases with frequency and becomes critical for printed circuits operating at frequencies above 200 or 300 Mhz. Impedance calculator software is a good starting point to determine the track width (w) and insulation thickness (h) of a given impedance. In terms of signal traffic in
a planar form, such as stripline or microstrip, with dimensions carefully controlled to ensure consistent impedance. In RF and fast switching circuits, the inductance and capacitance of the printed circuit board conductors become significant, HASL usually unwanted, circuit elements; rather, they can be used as part