1/2 oz vs 1 oz copper 1

[SamuraiMike]

Hi,
When etching microstrip antennas the board material is available in 1/2 oz vs 1 oz. Why do I choose one over the other? Thanks

 

[SamuraiMike]

I should say 1/2 oz copper clad vs 1 oz copper clad. There is also rolled vs electrodeposited, which I know affects the surface roughness and maybe loss/glue adhesion. Other things I should be aware of?

 

[BobM3]

Thickness of the copper will affect your impedance. Agilent's AppCAD freeware is useful for calculating the impedance of microstrip.

 

[MacGyverS2000]

Well, for one thing the different thicknesses change the strip dimensions, which can have a minor or major effect on your antenna specs, depending upon frequency of interest, bandwidth, etc. Pretty much every standard type of board is going to be rolled... why do you care about the construction process?

Dan - Owner

http://www.Hi-TecDesigns.com

 

[SamuraiMike]

The thickness of the copper only (not the board), at least near 1 GHz, doesn't have a huge affect on the line impedance. I went straight to the Rogers website and used their calculator for microstrip line and it only made ~1 ohm change. The actual board thickness of course makes a big difference. There is a current carrying capacity which changes with copper thickness, but it didn't seem to make a big difference in power handling...

 

[Higgler]

The primary reason for thinner copper is to etch thinner lines.
Say you want to etch 2 mil lines and your copper is 1.4 mils thick, there's alot of undercut in the etching process for that case. Your impedance will be inconsistent for thin lines in that case, and pretty good for wider lines.

For most patch antennas, 0.5 vs. 1 oz copper isn't too much of a difference.

electrodeposited cracks easier with vibe and cold, but etches cleaner and more accurately.

If you have a large patch array or interferemeter array at 18-40 ghz and use rolled copper, when the copper is etched away, your circuit board physically shrinks (or springs back) with rolled copper since the rolling of copper onto dielectric board (with heat) stretches the base dieletcric. You actually have to make artwork larger in dimension than you want to plan on the shrinkback.

Read Rogers corp. info for more details.

kch
khiggins@toyon.com

 

[biff44]

You would use the 1oz copper if you were working with higher power RF antennas. For standard microstrip work, 1/2 oz is used, as stated above, since it is easier to control the etch widths of.