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I have a crazy idea. What if you were to make a PCB with connectors soldered on both sides? The PCB is the air tight media for your solution and the connectors are the break outs for the connections. You can make the PCB the proper thickness for mechanical strength.
The connectors are soldered with through hole pins. The pads are filled with solder, so that's gas tight. Use a large pad size and hole size (i.e. lower aspect ratio) to improve on the seals between the pad and the PCB and the mechanical strength.
Additional backfill can be used on top of the solder joints if leakage due to thermal/expansion/contraction might be an issue. The connectors need to be offset so that they don't blocked the opposite side. The tracks etc are of course are done with controlled impedance with internal ground layers.
My original idea was with SMT connectors and vias that are backfilled, but the solder joints for the SMT connectors might cause problems for thermal cycles.
Registered Member #1667
Joined: Sat Aug 30 2008, 09:57PM
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Posts: 374
You mean these SMA connectors?
Connectors directly soldered to PCBs still give me a headache. Basically there is nothing wrong with the PCB "seal" solution buf I'm afraid of cold solder joints in hard-to-reach places. Let's assume SSMCX / UMCC connectors are used on the vacuum side, then an 5W5, 7W7 or 8W8 DSUB connector could be used on the outside:
By the way, I must again point out that the hot end connectors are only subject to minor thermal cycles ( 0.. 40°C).
If it is through-hole connectors on both side, the solder joints are visible and accessible. You can microscope the individual joints for voids/bad joints before installing this onto your equipment. Cold solder joint is a matter of process control on soldering temperature.
Not like you would use a Radio Shack non-temperature controlled 10W soldering iron for this. The thermal mass of the individual SMA pins aren't that bad if you do use thermal relief.
Registered Member #1667
Joined: Sat Aug 30 2008, 09:57PM
Location:
Posts: 374
Cold solder joints may also develop as fatigue cracks when the connector is mishandled. I wish I could improve stability by separating the connector from the vacuum seal. This would most likely have to be done with flexible PCBs to keep eveything nice and small. Is it just me or are things getting really complicated?
I thought about flex circuit, but don't like a flimsy solution. Card edge connector. Signal Integrity. LOL,
There are mounting holes on the two sides of your DSUB connector. If they are at least mechanically fasten down, they would reduce the amount of stress that your solder joints would see due to handling. You can also have a pigtail cable harness that is where the actual mating rituals take place.
Also the PCB assembly can be treated as a throw away. If you starts seeing problems, replace it with a new one. Don't even bother with debug etc.
Anyways, using PCB is just an idea that popped in my head. Of you are going down the path of a Circular connector, I would recommend a Bayonet over the non-Bayonet. You can feel the click as it locks in compresses the rubber seal.
On the other hand, the cable end assembly is "fun". I had to do make one end of the cable on site one time with customer looking over my shoulder and being cheap having to use the solder cup one with the rubber gasket over the solder joint. Let's say I have about 1 cm of space under the gasket to work with a soldering iron and not melt the rubber.
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approximating a multi-coax feedthrough?
