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| luudee:
Dear Lasmux, have you considered printing the enclosure from conductive ABS ? Kind Regards, rudi |
| lasmux:
I did consider a conductive enclosure. I didn't go for this as I was concerned about increased capacitive coupling to ground on the signal pin, which would negatively affect the return loss on probed lines. I really want to keep that 0.7pF input capacitance, which was very difficult to achieve. Another issue is that the enclosure is a very small print, and it has to interface with a real PCB. When I was prototyping I found that if the print wasn't dimensionally accurate enough, the PCB just wouldn't fit, especially around the probe tip socket area. Conductive ABS is normally printed via an FDM process which doesn't have the precision needed. Not to mention that FDM prints don't look as aesthetically pleasing as SLS prints. |
| tggzzz:
--- Quote from: lasmux on June 25, 2024, 01:11:44 pm ---I did consider a conductive enclosure. I didn't go for this as I was concerned about increased capacitive coupling to ground on the signal pin, which would negatively affect the return loss on probed lines. I really want to keep that 0.7pF input capacitance, which was very difficult to achieve. Another issue is that the enclosure is a very small print, and it has to interface with a real PCB. When I was prototyping I found that if the print wasn't dimensionally accurate enough, the PCB just wouldn't fit, especially around the probe tip socket area. Conductive ABS is normally printed via an FDM process which doesn't have the precision needed. Not to mention that FDM prints don't look as aesthetically pleasing as SLS prints. --- End quote --- Ignorant suggeston: could you use a conductive paint? I assume you could mask off the areas where you want to keep capacitance low. I've no idea about how well paint would or wouldn't adhere to the plastic, but it would be in the protected interior. The sintered nylon I've used is relatively rough (compared to SLA!), which might help. |
| lasmux:
--- Quote from: tggzzz on June 25, 2024, 01:30:28 pm --- --- Quote from: lasmux on June 25, 2024, 01:11:44 pm ---I did consider a conductive enclosure. I didn't go for this as I was concerned about increased capacitive coupling to ground on the signal pin, which would negatively affect the return loss on probed lines. I really want to keep that 0.7pF input capacitance, which was very difficult to achieve. Another issue is that the enclosure is a very small print, and it has to interface with a real PCB. When I was prototyping I found that if the print wasn't dimensionally accurate enough, the PCB just wouldn't fit, especially around the probe tip socket area. Conductive ABS is normally printed via an FDM process which doesn't have the precision needed. Not to mention that FDM prints don't look as aesthetically pleasing as SLS prints. --- End quote --- Ignorant suggeston: could you use a conductive paint? I assume you could mask off the areas where you want to keep capacitance low. I've no idea about how well paint would or wouldn't adhere to the plastic, but it would be in the protected interior. The sintered nylon I've used is relatively rough (compared to SLA!), which might help. --- End quote --- That could work tbh. The coating would have to be on the outside though as the enclosure at the front of the probe is not split into two (it's in one part) so you couldn't mask off the area near the front of the probe which is most susceptible to noise. As it's on the outside it would need to be reasonably aesthetically pleasing when applied. I've never tried to spray paint 3D printed parts before though. It sounds... time consuming... |
| joeqsmith:
Concerning printing conductive plastics and coatings, I was looking into this as a way to produce low cost waveguide parts. The video shows most of the end results. The last attempt was to use a high content copper filament then bake out the plastics. https://www.eevblog.com/forum/rf-microwave/experimenting-with-waveguides-using-the-litevna/msg4646872/#msg4646872 |
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