High reliability ribbon cables

[Retirednerd2020]

I have an application that includes interconnects with latching 100mil grid 2x13 PCB-mounted connectors on each end.  The PCBA connectors are gold plated.  The pre-made IDC ribbon cables that were purchased from (a trusted) distributor and manufacturer have proven to be very low reliability.  Out of 1726 in the field for <2 years, 78 have had intermittent connections and were replaced.  The application is not challenging, clean, dry, low vibration, low stress and no movement.  I'm looking for a bullet-proof connector/cable to kill off the problem.  Some failed due to IDC issues and others due to contact issues.  Cost is not a high priority.

Anyone have suggestions on type of connector / brand with proven reliability?  Individual wire connectors are not out of the question if they are any better.

[coromonadalix]

normally going gold plated is the best choice,  but exterior uses has it's limits  even  low stress etc .... 

i add mineral grease in the pins, 

and normally use idc connectors with lock / latchs and add a tie wrap to maintain them closed .... or a dab of sillicon

done that in more stressed out electronics   like leds panels running 24/24   all seasons for at least 5 years now ??

[Retirednerd2020]

I don't know why I have had such a time with this batch of ribbons.  It seems like a solved problem but maybe a bad run of them or something?  The connectors are gold plated.  What sort of coating did you use specifically?  Again, the application is about as benign as you can imagine.

[Ian.M]

See https://www.molex.com/en-us/blog/gold-or-tin-vs-gold-and-tin
If the pins in the header are gold plated, the sockets in the IDC connector must be gold plated where they fit over the pin but if the end with the IDC blades that pierce the cable is gold plated, it will be less reliable as the wire strands are usually tin plated.  If they are entirely gold plated, you probably need silver plated wire.

Also, the IDC connector strain relief bars should be properly fitted.

[tooki]

Ribbon cables are used widely, the vast majority likely el-cheapo junk, without problems. Back before SATA, every computer’s hard drives and floppy drives used them. Your failure rate is almost 5%, which is very obviously exceedingly high.

I see a few potential sources for the problem, in no particular order:
- a faulty production run of the connectors themselves
- improper storage of the connectors before assembly
- faulty assembly of the connectors onto the cable
- improper handling of the finished cable assemblies

What I think is less likely, since you said some of the failures are contact failure, is bad cable, or a mismatch between cable type and connector type.

How did the failures manifest, by the way? I.e. what are the symptoms and troubleshooting steps that led to your diagnosis of the two failure modes?

[coppercone2]

what is breaking

is it the IDC joint, meaning
-bad crimp tool
-dirty connectors that won't cold weld
-dirty wiring tht won't cold weld
-bad plating not compatible with cold welding

or is it plating on the interconnect (pin fit) end
-uncleaned before plating bath
-dirty plating bath
-low plating bath time(thin gold)

or is it the alloy
-deforming because its not springy enough

or is the pin on your end bad messing up the connector


could be wire that got wet and corroded, the connector that did the same, the tool is all fucked up, or it was made wrong in the factory

those IDC pins are cold welded into a fork, its not like any crimp that we normally use. unique technology. small bond area, high enough pressure to cold forge a connection together via massive point pressure. i hate IDC. wire wrap with 1/2 loop  . The technology it was based on used around what, 4-6 turns around a post to ensure a cold welded connection>? this just jams it into a groove. And also wire wrap = solid wire, IDC people use it on stranded wire! IMO the interconnect is seriously dodgy

[tooki]

If the pins in the header are gold plated, the sockets in the IDC connector must be gold plated where they fit over the pin but if the end with the IDC blades that pierce the cable is gold plated, it will be less reliable as the wire strands are usually tin plated.  If they are entirely gold plated, you probably need silver plated wire.

I think you’re imagining a theoretical problem that doesn’t exist. Manufacturers have been moving away from allover gold plating for years to save money, and certainly wouldn’t be spending the money to apply it to parts of a contact where its presence would be detrimental!

Not that I believe gold-to-tin/copper/silver in the contact-to-wire interface to be a real problem anyway: if it were, the military would not allow gold plating on the crimp surfaces of military connectors. But not only is it allowed, it’s specified.

The problems with gold-on-tin that the linked article discusses are with the mating surfaces, which experience movement across each other during mating, and in subsequent vibration. None of that applies to the crimped interface, nor IDC.

Anyhow I checked the most expensive IDC connectors on DigiKey and their drawings expressly show gold only on the contact mating surfaces, not the IDC forks.

[coppercone2]

you can't have it in the fork because then you get some gold intermetallic in the cold weld that is contamination afaik

[tooki]

those IDC pins are cold welded into a fork, its not like any crimp that we normally use. unique technology. small bond area, high enough pressure to cold forge a connection together via massive point pressure. i hate IDC. wire wrap with 1/2 loop  . The technology it was based on used around what, 4-6 turns around a post to ensure a cold welded connection>? this just jams it into a groove

The countless billions of PCs made using hundreds of IDC connections each, and the billions of IDC (or “punchdown”, ad they call it in that industry) connections made in copper telephone wiring and every wall-mounted Ethernet jack, prove that IDC is actually a highly reliable technology.

[tooki]

you can't have it in the fork because then you get some gold intermetallic in the cold weld that is contamination afaik

I literally just disproved the importance of that in cold-welded connections because of military crimp connectors.

[coppercone2]

imo it means people throw away pc because its getting outdated every 3 months and we throw it out

telecom wire is single strand. at least the runs that are never breaking are. the stuff in your house is not reliable. infact in the -80s90's you could save alot of money if you redid your own phone sockets. good tool to have...

if you are doing a cable run to a outlet in your wall, go with single strand for the IDCtype connectors!

you found a military grade IDC connector? a typical crimp does not cold weld. only the IDC fork does.
this is what the IDC fork is trying to do on a massively small surface area of the tiny fork



unless your removing tons of flash from doing a crimp, your not getting a cold weld. that requires significant displacement. the fork might do it a little bit.
a wire wrap and wire nut do this a little bit on the sharp point of the post or interconnect (square edge hard bronze)

nothing in a standard crimp is going to be unyielding or sharp enough to get that real cold weld action going

[tooki]

imo it means people throw away pc because its getting outdated every 3 months and we throw it out

Stop with the hyperbole. People do not throw out their computers every 3 months. Not now, and not 25 years ago.

I used to work as a computer technician. IDC cable failure was exceedingly rare, and almost always due to someone pulling on it to unplug it.

you found a military grade IDC connector? a typical crimp does not cold weld. only the IDC fork does.
this is what the IDC fork is trying to do on a massively small surface area of the tiny fork

I didn’t say a military IDC connector, I said a military crimp connector. (Though I wouldn’t be surprised if they exist, too.)

nothing in a standard crimp is going to be unyielding or sharp enough to get that real cold weld action going

Well that’s news to the crimp connector industry, which does say that crimping causes cold welding.

[coppercone2]

ok and I also worked with computers and I think ribbon cables are shit and good riddens . SATA has a nice wide area crimp or a solder joint unlike pITA connectors

as for the other thing "industry" says alot of things

the only things that are cold welding is that machine, forks, wire wraps and wire nuts (maybe)


you think those forks in the telephone thing will deform like a regular crimp? they are FUCKING hard .Same for wire wrap. BRonze. destroys side cutters ez.

maybe find the spec for a military bunker telecom run, that might actually be relevant

its the concept of using a hammer and an anvil


i took apart a telephone IDC thing. the first thing I noticed is that the metal for the little forks aint soft. if you run a tool across them you will notice it feels off and ringy because its really god damn tough

[Retirednerd2020]

In response to some of the feedback:

The cables were purchased complete from a distributor.  They are 3M M3DDA-2606.  The mating connectors are gold plated too.  The cables were taken out of packaging, clicked into the latching connectors.  Mishandling would be unlikely.  The equipment was built, stored and operated in dry, air-conditioned conditions. 

The problem manifested in disrupted signals or power in one or more pins.  The problem was typically intermittent.  It was found that wiggling the connector could cause an intermittent connection to fix itself.  The connectors were in-line with each other so no twisting or torque on the ribbon at all during operation.  Solder connections of the male headers to the PCB were checked and found good.

[tooki]

ok and I also worked with computers and I think ribbon cables are shit and good riddens . SATA has a nice wide area crimp or a solder joint unlike pITA connectors

as for the other thing "industry" says alot of things

[rabble rabble]

Forgive me if I choose to believe what is taught in the electronics industry, and not what one perpetually-angry, often-incoherent forum member (you) says on the matter.

[coppercone2]

you start shit here like its a paid job and you basically gave no support other then some shadowy electronics industry marketing hearsay

[tooki]

The cables were purchased complete from a distributor.  They are 3M M3DDA-2606.  The mating connectors are gold plated too.  The cables were taken out of packaging, clicked into the latching connectors.  Mishandling would be unlikely.  The equipment was built, stored and operated in dry, air-conditioned conditions. 

That appears to be a DigiKey part number — other distributors don’t know it. And the first datasheet is the DigiKey custom cable form, and the part is listed as a DigiKey value-added part, which is something made by DigiKey (presumably with 3M’s blessing, as many connector companies do, having certain distributors assemble things for them). Anyway, have you raised the issue with 3M and DigiKey? Even if they don’t offer replacements at this point, they may be interested in an “engineering capture” of the failed parts to figure out what went wrong.

The problem manifested in disrupted signals or power in one or more pins.  The problem was typically intermittent.  It was found that wiggling the connector could cause an intermittent connection to fix itself.  The connectors were in-line with each other so no twisting or torque on the ribbon at all during operation.  Solder connections of the male headers to the PCB were checked and found good.

OK, but you didn’t answer my final question: how did you diagnose the TWO failure modes?

[Ian.M]

The cables were purchased complete from a distributor.  They are 3M M3DDA-2606.  The mating connectors are gold plated too. 

Well, that rules out far east fake connectors with contacts made of mystery metal and thin purely cosmetic gold plating.

[tooki]

you start shit here like its a paid job and you basically gave no support other then some shadowy electronics industry talk

Believe what you want. I’m not the one who constantly rants about everything, and typically replies with borderline incoherent writing.

And I have been giving the OP support, you’re just pretending it’s not there. That’s a “you” problem.

[jonpaul]

Take the issues to the Disty.
Return if possible

Perhaps used poor qual connectors, cables or tooling

j

[Retirednerd2020]

Anyway, have you raised the issue with 3M and DigiKey?

I informed Digikey.  I'm not interested in returning etc.   I just thought they could make good use of the feedback.

I appears to be about 90% a problem on the insulation displacement side, maybe even 100%.  It is hard to tell.  I did a lot of wiggling of connectors while trying not to disturb the cable, etc.  Not too scientific but it was what I had time for at the time.  These things don't come on all at once.  It was one here and one there but they added up.  At this point, after due consideration, I'm leaning toward poor assembly of "good" parts.  Could be wrong.  All the cables I've had replaced over the last year or so have been fine.  I've used the same part number.

My question was mostly forward-looking as in what do I ship the product with to avoid this potential issue?  Possibly the answer is to stick with the same part but if there is a component designed with higher inherent reliability, I would go with that.

As to the arguments above, please don't get too worked up.  It is only a cable and I will solve the problem one way or the other.  I appreciate all the well meaning input.

Regards,  RJ

[robert.rozee]

could it be good 3M connectors, but some dodgy supplier of the actual ribbon? is "3M" printed on the ribbon?

i usually check cables with a magnet, it is not unknown these days to encounter strands of wire made out of steel with a copper plating. i first noticed this around 10 years back, when a cable brushed against a magnet and stuck!


cheers,
rob   :-)

[Retirednerd2020]

Good thought rob.  Thanks.  Noticed your NZ location.  I think my Sister and Brother in law are in Picton or Wellington today on a cruise.  Say "Hi" for me if you see them.   

[jmelson]

In response to some of the feedback:

The cables were purchased complete from a distributor.  They are 3M M3DDA-2606.  The mating connectors are gold plated too.  The cables were taken out of packaging, clicked into the latching connectors.  Mishandling would be unlikely.  The equipment was built, stored and operated in dry, air-conditioned conditions. 

The problem manifested in disrupted signals or power in one or more pins.  The problem was typically intermittent.  It was found that wiggling the connector could cause an intermittent connection to fix itself.  The connectors were in-line with each other so no twisting or torque on the ribbon at all during operation.  Solder connections of the male headers to the PCB were checked and found good.

Wow, this is extremely odd!  I have built tons of equipment with 34-pin ribbon cable, I always use gold-plated headers and connectors.  We have had problems with the outermost wires of the ribbon going bad after many connect/disconnect cycles if the cable is not folded over and clamped with the strain relief.  I prefer CW brand connectors with the metal strain relief bar.  It is extremely rare to get a bad contact on these with the strain relief.
I don't know if whoever made the cables did something wrong (new guy, first day on that job) or whether there was a manufacturing defect.  It is kind of a miracle that this IDC stuff works at all, there must have been TONS of trial and error to get reliable connections.
Jon

[BennoG]

you mentioned the power pins, what kind of power you are talking about in mA or A

Benno

[toybuilder]

Were your cable suppliers involved in the selection of the mating socket connectors? 
If both socket and plug were from the same manufacturer, you might want to contact the manufacturer's rep -- at 1726 (x2) units, there's enough volume for them to at least take your call.

[jmelson]

Ohh, I thought of another possible cause.  How were the headers soldered to the boards?  Were they wave soldered?  Or, were the boards cleaned after soldering?  Some wave solder processes get flux sprayed all over the place.  If flux got on the header pins, and/or the boards were not completely cleaned of all flux residue, then flux on the pins could cause delayed failure and intermittent contact.  Generally, wiggling the connector might "fix" it for a few days, but then it might fail again.
Jon

[Retirednerd2020]

Responding to other comments:

The power pins are maybe 30mA-50mA at worst.

The boards were cleaned as part of the specified processing.  The gold pins looked clean on visual inspection but may have a closer look.

I don't know how the manufacturer chose the cable to go with the connector.  I do know that they are reputable in general.

[Smokey]

It's hard to fix a problem you don't know the root cause of.  X-ray a fault cable maybe?

Make a revision for the cable assemblies with different everything (cables, connectors, mates, and assembly). There are about a million options for 0.1in ribon cable parts and assembly.  Instead of IDC, use individual wires and crimp pins?

[tooki]

Y’all…

Perhaps used poor qual connectors, cables or tooling

could it be good 3M connectors, but some dodgy supplier of the actual ribbon? is "3M" printed on the ribbon?

Were your cable suppliers involved in the selection of the mating socket connectors? 
If both socket and plug were from the same manufacturer, you might want to contact the manufacturer's rep -- at 1726 (x2) units, there's enough volume for them to at least take your call.

Am I the only person who bothered googling the part number?!?

It resolves to two variants of Digikey custom cable assembly, one with gray cable, one with rainbow cable:
Gray: https://www.digikey.ch/en/products/detail/3m/M3DDA-2606J/230229
Rainbow: https://www.digikey.ch/en/products/detail/3m/M3DDA-2606R/230228

On the product page, it has a BOM of the components used to make the assembly: two connectors, two strain reliefs, and a length of cable.

So we know exactly what connectors and cable they used, down to the part number. It’s not whatever random cable a procurement bean counter managed to scrounge up that week. 

[thermistor-guy]

...  Out of 1726 in the field for <2 years, 78 have had intermittent connections and were replaced.  The application is not challenging, clean, dry, low vibration, low stress and no movement...

I use 3M twisted pair ribbon cable with Harting IDC DIN41612 connectors (64-way), in  test jigs. The combination has proven reliable, but there is a fault that
can occur during initial cable assembly.

The cable can sometimes have a distorted conductor-to-conductor pitch, so that it doesn't line up exactly with the IDC connector tines.
If the misalignment is bad enough, it results in adjacent conductor short-circuits.

Conceivably, if the misalignment is not that bad, but still present, it could lead to unreliable conductor-to-tine contacts; contacts that are not
gas-tight and that will fail over time.

To guard against this, I check the cable alignment against the IDC before assembly, then check for continuity and no adjacent shorts after.
Sometimes I do have to massage (stretch or compress) the ribbon cable into good alignment, beforehand.

[mkiijam]

I think your "trusted supplier" of predone IDC cable use cheap alternative to real (expensive) crimping tool.

[tooki]

I think your "trusted supplier" of predone IDC cable use cheap alternative to real (expensive) crimping tool.

Very unlikely. DigiKey is not some el-cheapo fly-by-night operation. I would expect their agreements with 3M require them to use the official tooling, not to mention that the volumes they do pretty much preclude using cheap manual tools.

[thm_w]

Do you have the ones in hand that were replaced? Inspect them, there may be some strain that occurs that you didn't think about.

Could consider getting someone other than Digikey to build them. A company that will do resistance and hi-pot tests, etc. I don't know if digikey does this, I don't see anything specifically advertised on their site.

Very unlikely. DigiKey is not some el-cheapo fly-by-night operation. I would expect their agreements with 3M require them to use the official tooling, not to mention that the volumes they do pretty much preclude using cheap manual tools.

Most likely you are right, but I'd like to see some video evidence out of curiosity, I can't find anything on their site other than just spooled wires that they cut by hand.
https://www.youtube.com/@digikey/search?query=cable