layer stackup matched impedance
Hi,
First, the stack layer is decided depending on the type of your application. If you application is at low speed, not sensitive to noise, than you can use simple or double plated board. If you app is high frequency analog, digital or mixed, then the things will complicate. You have to use multilayer boards with ground and power planes. The mechanical details of the board (thickness for plating, dielectric, prepreg, min hole size, min track size, max number of layers), all these you should discuss with your pcb manufacturer, each manufacturer has its own limits. Most of the manufacturers who have a website will offer these informations on site. The trace width is important from two points of view. When the signal which pass a trace is low frequency but high current, the trace must be wide enough to withstand the current density. For high speed and rf signals, the trace width (along with other factors - dielectric constant, dielectric thickness, working frequency, and others) will determine the characteristic impedance of the track. In your post, I think you meant "imedance of a track" not "impedance of the board". It is important to use matched impedance transmission lines between diffrent parts of your design, in order to avoid signal reflections, which can affect the functionality of your design. You can find more informations on this forum, search at ebooks after "signal integrity" or "pcb rf design" or similar. A good tool to calculate the impedance of a track is appcad from agilent. It is free.