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Gadgeteer 10-way IDC connector reliability


#1

We have been having some issues with the 10-way IDC connectors, and our findings may be useful to others.

We started getting returns from the field with intermittent connections, for the first few it was put down to a bad crimp, a broken core in the ribbon cable, or perhaps a bad solder joint on the SMT part, and they were just replaced. However as more came in with the same problem, we had to establish just where the failure was.

It appears that although the two plastic parts mate securely, if the ribbon cable is moved then the metal “socket” parts that pierce the ribbon and connect with the individual wires also move slightly within the plastic housing.
Over time this movement seems to weaken the socket’s spring force against the mating pin, resulting in an intermittent connection.

In our case there can be a slight (only a few degrees) movement of the ribbon relative to the PCB every time a reading is taken. With perhaps 12,000 readings a day, this can add up to millions of readings over a few months.

I don’t know if anyone else has seen this effect, it is possible that vibration could also cause it, if of sufficient magnitude to take the connector spring outside its elastic limit.

I designed a simple strain relief clip and printed a few out on the 3D printer, we are now going to field-test and see if that overcomes the problem for us.


#2

Great findings and thanks for sharing your experience with it.

Can you confirm whether these are on your own PCBs or others, and if your whether they’re the SAMTEC part or an equivalent? That info will probably help others greatly too !


#3

I’ve also seen this with the TE35 display I have and the connector for the touch.

The issue I see is that these connectors are not fitted with any form of strain relief. I used to use IDC connectors without many years ago but after getting some units back with cable failures, I stopped this practice and changed to the types with.

The problem with the gadgeteer sockets is that they are not designed to take any form of strain relief, you know, the types normally fitted to IDC connectors like the old IDE drive cables.

I’ve taken to using a hot melt glue gun to run a thin bead along the cable to connector on the top to reduce any flexing. Seems to be working so far as the TE35 touch still works :slight_smile:


#4

@ Brett - These are our own PCBs.

The connectors are FCI

The IDC part (attached to the ribbon) came from Mouser, part numbers:
FCI: 20021444-00010T1LF
Mouser: 649-200214440001T1LF

The SMT part (attached to the PCB) came from DigiKey, part numbers:
FCI: 20021521-00010T1LF
DigiKey: 609-4054-ND

I’ve attached an image of the restraining clip

[edit] The clip is pictured upside down. It presses down over the connector after the cable is inserted, holding the ribbon against the connector body. The ribbon comes out against the PCB at the bottom


#5

Neat, I like it. Any chance of uploading an STL file somewhere? (thingiverse maybe).


#6

its not completely clear where it is, can you provide an image?


#7

I’ve put an STL on CodeShare:

https://www.ghielectronics.com/community/codeshare/entry/856

Hopefully it will work there, if not I can change it from binary to an ASCII STL.

Reads the comments about the heuristic sizing - my slicing software (Slic3r) wasn’t behaving very well that day!