PCB design: thin pins to thick wire??

[tzahi]

Hi

I using AD8000 in SO8 package. which have pins of ~0.51 mm.
since I need to match the impedance (RF of ~1GHz) to 50 Ohm, I thought of using microstrip.
THE PROBLEM IS:
the PCB is FR4 that have: w=1.6mm Er=4.34@1GHz t=.5/1/2 Oz (t doesnt influence that much as I saw in calculators).
that obligating the microstrip wire to be ~3mm!!!
Is there a "tricky" way to connect the 3mm wire of PCB to the 0.5mm SMD???
Is there a certain way to connect them without damage the 50 Ohm "transmission line"??

an image that illustrate the proportion between the SO8, 0.5mm & 3mm is attached

thanks in advence,
Tzahi

 

[buenos]

hi.

Two things:

1. the wire can be narrower on the first 1-2mm of length, this is called breakout. This short segment will not disturb your signal too much, you don't need the calculated width all the way to the chip pad.

2. it looks like you want 50ohm on a 2-layer PCB. Maybe you should start thinking on using a thinner PCB, like 0.75mm thick to make your 50R tracks to be a lot narrower. If you are making your own PCB then it might be difficoult getting 0.5...1mm thick bare board. But if you get your PCB made at a PCB manufacturer then you can ask them what thicknesses are available in their stock and use one of those. These thin bareboards are used for manufacturing multilayer boards, and called core or laminate. If the GND plane is closer, then the impedance calculation results in a narrower track width for the same impedance value.

 

[raylay]

The short distance from the SMD pin which lost match 50 OHM will not effect the signal quality too much. Or you may adjust the stack, make your impedence trace thinner.