Straight or 90 degree MMIC input?
Dave created the topic: Straight or 90 degree MMIC input?
Has anyone ever tried putting a MMIC (die, not packaged) so that the RF wirebonds are at 90 degrees to the direction of the input (or output) trace?
Normally I think we all see them placed so that the bonds continue in the same direction as the trace, and intuitively this would seem to be the better approach.
Has anyone tried using the transition from trace to MMIC to implement a 90 degree bend? Successfully?
Desert Sage replied the topic: Straight or 90 degree MMIC input?
My experience is over 25 years ago. Some of the memories are hazy. The answer to your question is yes I've seen it done and done it.
However, two caveats come to mind. My experience was the shorter the bond wire the better. But assuming you have a good 50 ohm line close to the pad even at 90 degrees it shouldn't be an issue. We used to laser a hole (for the chip) in alumina to minimize bond lengths. A 50 ohm line running by that hole would be too high impedance due to missing dielectric and would need to be wider. Also, there is a greater chance to EM couple the MMIC to the line that may degrade performance.
Microwaves101 replied the topic: Straight or 90 degree MMIC input?
The only times I recall seeing this is when a SPDT switch had both poles exiting on the same side of the chip. If you came out with parallel lines the coupling would kill you, so the 90 degree turn (or just a 45) was the best approach. MMIC switch designers, don't do this ever again please....
The higher up in frequency (a la mmw), the less likely this will be a good idea.
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