Conformal Coating on IDC Ribbon Cable Connector?

[SCOC]

I am using an IDC type ribbon cable connector (TE 2-746610-4)in a fairly dusty/dirty environment. We have been conformal coating the connector, including top holes, on the assembly after the cable is crimped in of course. Our manufacturer is now saying that it could be an issue if the coating creeps inside compromising the connection. We specify Humiseal 1B73, 1A-20, or 1A-33. We have not had any issues up to this point. Is there an issue continuing this process, or a better way of coating the connector?

Thanks

 

[MikeHalloran]

If the coating is creeping into the connector, it has to be filling voids that would otherwise be full of air, which is a known corrodent of electrical connections.

You are probably better off with something other than air in the voids.



Mike Halloran
Pembroke Pines, FL, USA

 

[BrianG]

Quote:......after the cable is crimped in of course
IDC ribbon connections are not really crimped: the tines just cut through the wire insulation on each side, so not a wonderful contact. Has this comment from the manufacturer arisen because you have referred back about reliability problems?

 

[itsmoked]

I wouldn't expect any issues from that as long as you are coating only after complete assembly of the header onto the ribbon and the header is plugged into its mate. If you're coating the flying cable w/ header then eventually plugging into the mate... that would be bad.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[btrueblood]

Not sure what benefit a coating would have against dust, as there will always be a gap along the faying edges of the connector and header. Unless there is a gasketed version of the plug I haven't seen?

 

[IRstuff]

Conformal coatings are really intended to prevent corrosion of metallic components. The typical ribbon connector contacts are supposedly gas-tight, so the conformal coating ought not be capable of displacing the metal blades.

If the connector is never exercised, there ought not be any need to conformal coat, unless there is possible corrosion.

TTFN
faq731-376

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[btrueblood]

I was ASSuming they were trying conformal coating to reduce short circuiting of traces/contacts on the boards and connectors due to dust/contaminant bridging. Probably would be good to find out from the OP what exactly they are trying to fix, as Brian asked earlier.

The IDC ribbon cable connectors we use have a gap that can be opened up about 1mm between the socket and plug by pulling up on the plug until the clips stop that motion. You can then clearly see the exposed pins...so what does that mean for conformal coatings and gas tight sockets, for either moisture or dust penetration? Maybe pull the connectors open and then apply coatings? I'd not trust a typical spray to penetrate and coat the exposed pins - maybe a gas phase coating like parylene would work.

 

[LionelHutz]

We tried coating over IC's installed in chip sockets (both DIP and PLCC) and they would often lose contact after a period of time. I expect the same could happen with a ribbon connector.

 

[SCOC]

Thanks for the replies. This connector is direct wire to board, impossible to disconnect/reconnect after coating. Product uses forced air cooling which contains dust and other contaminents, so we are trying to keep as much as possible out from corroding the contacts. We've experienced no issues with doing this yet, but we just switched manufacturers and they have this concern. We've always done this, maybe we don't need to, but based on the feedback I've gotten and my past experience I don't see any reason to stop. I've inquired with the connector manufacturer engineers to see what they recommend regarding coatings, but have not gotten a response yet.