Re: QRP PA devices for 10 GHz

Neil Smith G4DBN

I'm going to try a PCB with 0.3 mm PTH in a tight pattern, solder it to the spreader first, let it cool, then use a stencil to fill the holes with paste and put the whole assembly in my oven for reflow. Another approach is to get the PCB fab to fit the devices, then  use low temp solder to fix the PCB to the spreader. If the two-step process isn't successful, I'll go one-step for the while thing.  When that fails, I'll go back to silver epoxy.

I haven't decided what connectors to use yet.  I have some tab-launch SMAs rated to 27 GHz, but I think I prefer the idea of these: which are cheaper than the Amphenol SV Microwave versions.

I wonder if using GCPW lines for the RF connections might mean I can use solder resist over the lines so I can solder the connectors at the same time as the components. I'll have a chat to my friendly neighbourhood CPWG expert. Doubtless everyone will say I will get away with ENIG or HASL on FR4, but where's the fun in that?  I know there are others working on designs using the same little chip and they are certain to be better than my feeble attempts.

I have other stuff to get finished first though. LOTS of other stuff.

Neil G4DBN

On 09/05/2021 01:13, Greg - ZL3IX wrote:
Looks like just the sort of thing I'm looking for, Neil, although, as you say, dissipating the heat will be a serious challenge. I'm not sure how to go about that, and will have to do some research on the thermal resistance of vias. I guess it would need a copper heat spreader, which would need to be pre-heated before attempting to solder the device. That's all new territory for me! Luckily one appears to be able to use the internal reference diode as a temp sensor, so at least the device can be shut down when too hot.

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