VIA sizes

[Philip Newman]

Hi, I am designing a filter multiplexer on microstrip in Agilent's
ADS. At the top of the structure is a filter section that is
grounded. the last transmission line has dimensions W=169690mm
L=0.732294mm.

My question is this: To be grounded properly, the design can either
be taken to the edge of the substrate (where it can make contact with
the ground plane of copper) or a via can be drilled through the
substrate to the copper.

Question 1: Which option is better?
Quesiton 2: What dimensions of via's are available ie what do
manufacturers like to work with....

I am currently designing with a tapered via with D1=0.15mm and
D2=0.25mm

Any ideas and help would be most appreciaited

Phil

 

[Patrick Bolton]

Philip,

In the past I've used vias BUT you must think about the actual layout. If
the via sits in the middle of the track there must be a section of copper
after the via. I added the small length of track that exists after the via
into my model. It did seem to make a difference on some 1.5 GHz bandpass
filters I made.

Regards

Patrick

 

[Philip Newman]

Hi, this is right at the end of the transmission line, so there is nothing
after it. ive been told that you can just drill through the substrate, and
the bigger the hole, the better, but it is important to work out the angle,
as the larger hole as at the top, and this will bring the ground plane
closer to the microstrip, so the critical angle is needed.

phil