I am looking for a system to interconnect several PCBs with an audio signal. The connection should be low capacitance and able to withstand 3kV peak...
Max cable length say 6 inch.
I'd like something like the small SMA connectors all those hams use. They use them at multi-GHz frequencies so I assume the connector and coax are low capacitance.
Not sure what voltage they can withstand; the data sheets don't talk about that.
Or any other possibility?
Jan
Max cable length say 6 inch.
I'd like something like the small SMA connectors all those hams use. They use them at multi-GHz frequencies so I assume the connector and coax are low capacitance.
Not sure what voltage they can withstand; the data sheets don't talk about that.
Or any other possibility?
Jan
Does not look like the SMA connectors will work: SMA RF Connector Specifications and Interface Dimensions | Amphenol RF
I'll second that - 3kV is a really high breakdown value. These days, connectors are getting smaller and smaller, and signal voltages are getting lower and lower, so I suspect that nothing commercially available will suit your purposes.
If you really need 3kV breakdown, I'd say you're best off trying to arrange some sort of contact system within an insulator that can handle the high voltage, probably some sort of glass or ceramic. Alumina or aluminum nitride are fairly common these days because of their use as substrates for high power LED circuits. You can get those materials with direct bonded copper, sort of like raw FR4 PCB material, etch your terminal arrangement onto that substrate, and solder some sort of suitable pin / socket parts onto those and probably get what you want, similar to how they used to make old ceramic hybrids.
The big difference from normal PCB layout is that for 3kV, you'll need to allow significant conductor spacing and also clean the assembly and possibly pot it or encapsulate it after you put it together. Yes, this is sort of exotic, but again, because of the increasing use of high power LEDs, people are using alumina and aluminum nitride for PCBs much more often these days, so it isn't so hard to get something like that commercially fabricated.
If you really need 3kV breakdown, I'd say you're best off trying to arrange some sort of contact system within an insulator that can handle the high voltage, probably some sort of glass or ceramic. Alumina or aluminum nitride are fairly common these days because of their use as substrates for high power LED circuits. You can get those materials with direct bonded copper, sort of like raw FR4 PCB material, etch your terminal arrangement onto that substrate, and solder some sort of suitable pin / socket parts onto those and probably get what you want, similar to how they used to make old ceramic hybrids.
The big difference from normal PCB layout is that for 3kV, you'll need to allow significant conductor spacing and also clean the assembly and possibly pot it or encapsulate it after you put it together. Yes, this is sort of exotic, but again, because of the increasing use of high power LEDs, people are using alumina and aluminum nitride for PCBs much more often these days, so it isn't so hard to get something like that commercially fabricated.
Thanks, I didn't find those voltage ratings. So, they are out...
There is a header system using 0.5 inch pitch that can be used up to 10kV. I was hoping I could find something that I could use with coax as a screened connection.
There is also a variant of the well-known BNC system (BNC-HV) useable up to 10kV, but that's expensive and bulky.
https://www.radiall.com/products/rf-coaxial-connectors/bayonet-connectors/bnc-ht-mhv.html
Jan
If you are going to have 3kV signals then you are entering a really specialist area of layout, if its for 3kV surges then its a different matter and normal rules tend to apply with some protection where signal enter a board.
I did a high voltage layout (only 2.5kV) for high voltage ION guides on several boards... not for the faint hearted. All creepage and clearance from IPC-2221...
IPC-2221B PCB Trace Spacing / Clearance by Voltage
As to connectors you probably need to look at MVH or SVH types for such voltages...
Some interesting notes, especially interesting is micro voids.
http://www.magazines007.com/pdf/High-Voltage-PCDesign.pdf
I did a high voltage layout (only 2.5kV) for high voltage ION guides on several boards... not for the faint hearted. All creepage and clearance from IPC-2221...
IPC-2221B PCB Trace Spacing / Clearance by Voltage
As to connectors you probably need to look at MVH or SVH types for such voltages...
Some interesting notes, especially interesting is micro voids.
http://www.magazines007.com/pdf/High-Voltage-PCDesign.pdf
Lemo's are definitely an attractive option except for the price...
My signal level is 1.5kV RMS so for safety I want to use material specced for say 3kV.
The MVH or SVH BNC's would be good, but as far as I can see they do not have a PCB-mount jack version. My need is for PCB-to-PCB connectivity.
The search goes on.
Jan
My signal level is 1.5kV RMS so for safety I want to use material specced for say 3kV.
The MVH or SVH BNC's would be good, but as far as I can see they do not have a PCB-mount jack version. My need is for PCB-to-PCB connectivity.
The search goes on.
Jan
Yes. For the external connections I plan to use SHV BNC connections.
But I need to bring the HV signal from the VAS board to the output stage board, that was what the search was for.
What I will probably use is the Molex KK system, which is a locking, polarized, 3.96 mm (0.156") pitch system: http://www.mouser.com/ds/2/276/0417910833_PCB_HEADERS-229084.pdf.
I use that for the HV supply, a 4-pin KK with the two middle pins removed.
I can use a 3-pin with the middle pin removed for the HV audio internally.
Jan
You may have to have some slots (greater than 1mm) between pins and copper features to get the required creepage distance, this is always greater than the clearance distance.
For all spacing calculations you have to use the peek voltage NOT the RMS so for your design you need to look at spacing for 2,200V.
My advice would be to design a multi-layer board and have ALL the high voltage tracks on the inner layers, then you can get away with 4.5mm clearance between conductors. This makes the design far safe rand is a technique used often where these sort of voltages are present.
The PDF shows the relevant page for calculating these spaces... For external conductors (tracks) I would use the figures from the B2 column even if solder resist is used, as solder resist is not A conformal coating and can have voids. This provides the highest degree of safety but for this design gives 11mm clearance, using B4 which would be acceptable gives 6mm clearance between any trace covered by solder resist on an external layer. Pads and connector pins so the B2 requirement has to be used for these...
For all spacing calculations you have to use the peek voltage NOT the RMS so for your design you need to look at spacing for 2,200V.
My advice would be to design a multi-layer board and have ALL the high voltage tracks on the inner layers, then you can get away with 4.5mm clearance between conductors. This makes the design far safe rand is a technique used often where these sort of voltages are present.
The PDF shows the relevant page for calculating these spaces... For external conductors (tracks) I would use the figures from the B2 column even if solder resist is used, as solder resist is not A conformal coating and can have voids. This provides the highest degree of safety but for this design gives 11mm clearance, using B4 which would be acceptable gives 6mm clearance between any trace covered by solder resist on an external layer. Pads and connector pins so the B2 requirement has to be used for these...
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.